| Message ID | 1606533966-22821-1-git-send-email-hemantk@codeaurora.org (mailing list archive) |
|---|---|
| Headers | show |
| Series | userspace MHI client interface driver | expand |
Hi Hemant, On Fri, Nov 27, 2020 at 07:26:06PM -0800, Hemant Kumar wrote: > This MHI client driver allows userspace clients to transfer > raw data between MHI device and host using standard file operations. > Driver instantiates UCI device object which is associated to device > file node. UCI device object instantiates UCI channel object when device > file node is opened. UCI channel object is used to manage MHI channels > by calling MHI core APIs for read and write operations. MHI channels > are started as part of device open(). MHI channels remain in start > state until last release() is called on UCI device file node. Device > file node is created with format > > /dev/mhi_<mhi_device_name> > > Currently it supports QMI channel. > Thanks for the update. This patch looks good to me. But as I'm going to apply Loic's "bus: mhi: core: Indexed MHI controller name" patch, you need to update the documentation accordingly. > Signed-off-by: Hemant Kumar <hemantk@codeaurora.org> Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org> Thanks, Mani > --- > drivers/bus/mhi/Kconfig | 13 + > drivers/bus/mhi/Makefile | 3 + > drivers/bus/mhi/uci.c | 665 +++++++++++++++++++++++++++++++++++++++++++++++ > 3 files changed, 681 insertions(+) > create mode 100644 drivers/bus/mhi/uci.c > > diff --git a/drivers/bus/mhi/Kconfig b/drivers/bus/mhi/Kconfig > index da5cd0c..5194e8e 100644 > --- a/drivers/bus/mhi/Kconfig > +++ b/drivers/bus/mhi/Kconfig > @@ -29,3 +29,16 @@ config MHI_BUS_PCI_GENERIC > This driver provides MHI PCI controller driver for devices such as > Qualcomm SDX55 based PCIe modems. > > +config MHI_UCI > + tristate "MHI UCI" > + depends on MHI_BUS > + help > + MHI based Userspace Client Interface (UCI) driver is used for > + transferring raw data between host and device using standard file > + operations from userspace. Open, read, write, poll and close > + operations are supported by this driver. Please check > + mhi_uci_match_table for all supported channels that are exposed to > + userspace. > + > + To compile this driver as a module, choose M here: the module will be > + called mhi_uci. > diff --git a/drivers/bus/mhi/Makefile b/drivers/bus/mhi/Makefile > index 0a2d778..69f2111 100644 > --- a/drivers/bus/mhi/Makefile > +++ b/drivers/bus/mhi/Makefile > @@ -4,3 +4,6 @@ obj-y += core/ > obj-$(CONFIG_MHI_BUS_PCI_GENERIC) += mhi_pci_generic.o > mhi_pci_generic-y += pci_generic.o > > +# MHI client > +mhi_uci-y := uci.o > +obj-$(CONFIG_MHI_UCI) += mhi_uci.o > diff --git a/drivers/bus/mhi/uci.c b/drivers/bus/mhi/uci.c > new file mode 100644 > index 0000000..fb9c183 > --- /dev/null > +++ b/drivers/bus/mhi/uci.c > @@ -0,0 +1,665 @@ > +// SPDX-License-Identifier: GPL-2.0-only > +/* Copyright (c) 2018-2020, The Linux Foundation. All rights reserved.*/ > + > +#include <linux/kernel.h> > +#include <linux/mhi.h> > +#include <linux/mod_devicetable.h> > +#include <linux/module.h> > +#include <linux/poll.h> > + > +#define MHI_DEVICE_NAME "mhi" > +#define MHI_UCI_DRIVER_NAME "mhi_uci" > +#define MHI_MAX_UCI_MINORS 128 > + > +static DEFINE_IDR(uci_idr); > +static DEFINE_MUTEX(uci_drv_mutex); > +static struct class *uci_dev_class; > +static int uci_dev_major; > + > +/** > + * struct uci_chan - MHI channel for a UCI device > + * @udev: associated UCI device object > + * @ul_wq: wait queue for writer > + * @write_lock: mutex write lock for ul channel > + * @dl_wq: wait queue for reader > + * @read_lock: mutex read lock for dl channel > + * @dl_pending_lock: spin lock for dl_pending list > + * @dl_pending: list of dl buffers userspace is waiting to read > + * @cur_buf: current buffer userspace is reading > + * @dl_size: size of the current dl buffer userspace is reading > + * @ref_count: uci_chan reference count > + */ > +struct uci_chan { > + struct uci_dev *udev; > + wait_queue_head_t ul_wq; > + > + /* ul channel lock to synchronize multiple writes */ > + struct mutex write_lock; > + > + wait_queue_head_t dl_wq; > + > + /* dl channel lock to synchronize multiple reads */ > + struct mutex read_lock; > + > + /* > + * protects pending list in bh context, channel release, read and > + * poll > + */ > + spinlock_t dl_pending_lock; > + > + struct list_head dl_pending; > + struct uci_buf *cur_buf; > + size_t dl_size; > + struct kref ref_count; > +}; > + > +/** > + * struct uci_buf - UCI buffer > + * @data: data buffer > + * @len: length of data buffer > + * @node: list node of the UCI buffer > + */ > +struct uci_buf { > + void *data; > + size_t len; > + struct list_head node; > +}; > + > +/** > + * struct uci_dev - MHI UCI device > + * @minor: UCI device node minor number > + * @mhi_dev: associated mhi device object > + * @uchan: UCI uplink and downlink channel object > + * @mtu: max TRE buffer length > + * @enabled: Flag to track the state of the UCI device > + * @lock: mutex lock to manage uchan object > + * @ref_count: uci_dev reference count > + */ > +struct uci_dev { > + unsigned int minor; > + struct mhi_device *mhi_dev; > + struct uci_chan *uchan; > + size_t mtu; > + bool enabled; > + > + /* synchronize open, release and driver remove */ > + struct mutex lock; > + struct kref ref_count; > +}; > + > +static void mhi_uci_dev_chan_release(struct kref *ref) > +{ > + struct uci_buf *buf_itr, *tmp; > + struct uci_chan *uchan = > + container_of(ref, struct uci_chan, ref_count); > + > + if (uchan->udev->enabled) > + mhi_unprepare_from_transfer(uchan->udev->mhi_dev); > + > + spin_lock_bh(&uchan->dl_pending_lock); > + list_for_each_entry_safe(buf_itr, tmp, &uchan->dl_pending, node) { > + list_del(&buf_itr->node); > + kfree(buf_itr->data); > + } > + spin_unlock_bh(&uchan->dl_pending_lock); > + > + wake_up(&uchan->ul_wq); > + wake_up(&uchan->dl_wq); > + > + mutex_lock(&uchan->read_lock); > + if (uchan->cur_buf) > + kfree(uchan->cur_buf->data); > + > + uchan->cur_buf = NULL; > + mutex_unlock(&uchan->read_lock); > + > + mutex_destroy(&uchan->write_lock); > + mutex_destroy(&uchan->read_lock); > + > + uchan->udev->uchan = NULL; > + kfree(uchan); > +} > + > +static int mhi_queue_inbound(struct uci_dev *udev) > +{ > + struct mhi_device *mhi_dev = udev->mhi_dev; > + struct device *dev = &mhi_dev->dev; > + int nr_desc, i, ret = -EIO; > + size_t dl_buf_size; > + void *buf; > + struct uci_buf *ubuf; > + > + /* > + * skip queuing without error if dl channel is not supported. This > + * allows open to succeed for udev, supporting ul only channel. > + */ > + if (!udev->mhi_dev->dl_chan) > + return 0; > + > + nr_desc = mhi_get_free_desc_count(mhi_dev, DMA_FROM_DEVICE); > + > + for (i = 0; i < nr_desc; i++) { > + buf = kmalloc(udev->mtu, GFP_KERNEL); > + if (!buf) > + return -ENOMEM; > + > + dl_buf_size = udev->mtu - sizeof(*ubuf); > + > + /* save uci_buf info at the end of buf */ > + ubuf = buf + dl_buf_size; > + ubuf->data = buf; > + > + dev_dbg(dev, "Allocated buf %d of %d size %zu\n", i, nr_desc, > + dl_buf_size); > + > + ret = mhi_queue_buf(mhi_dev, DMA_FROM_DEVICE, buf, dl_buf_size, > + MHI_EOT); > + if (ret) { > + kfree(buf); > + dev_err(dev, "Failed to queue buffer %d\n", i); > + return ret; > + } > + } > + > + return ret; > +} > + > +static int mhi_uci_dev_start_chan(struct uci_dev *udev) > +{ > + int ret = 0; > + struct uci_chan *uchan; > + > + mutex_lock(&udev->lock); > + if (!udev->uchan || !kref_get_unless_zero(&udev->uchan->ref_count)) { > + uchan = kzalloc(sizeof(*uchan), GFP_KERNEL); > + if (!uchan) { > + ret = -ENOMEM; > + goto error_chan_start; > + } > + > + udev->uchan = uchan; > + uchan->udev = udev; > + init_waitqueue_head(&uchan->ul_wq); > + init_waitqueue_head(&uchan->dl_wq); > + mutex_init(&uchan->write_lock); > + mutex_init(&uchan->read_lock); > + spin_lock_init(&uchan->dl_pending_lock); > + INIT_LIST_HEAD(&uchan->dl_pending); > + > + ret = mhi_prepare_for_transfer(udev->mhi_dev); > + if (ret) { > + dev_err(&udev->mhi_dev->dev, "Error starting transfer channels\n"); > + goto error_chan_cleanup; > + } > + > + ret = mhi_queue_inbound(udev); > + if (ret) > + goto error_chan_cleanup; > + > + kref_init(&uchan->ref_count); > + } > + > + mutex_unlock(&udev->lock); > + > + return 0; > + > +error_chan_cleanup: > + mhi_uci_dev_chan_release(&uchan->ref_count); > +error_chan_start: > + mutex_unlock(&udev->lock); > + return ret; > +} > + > +static void mhi_uci_dev_release(struct kref *ref) > +{ > + struct uci_dev *udev = > + container_of(ref, struct uci_dev, ref_count); > + > + mutex_destroy(&udev->lock); > + > + kfree(udev); > +} > + > +static int mhi_uci_open(struct inode *inode, struct file *filp) > +{ > + unsigned int minor = iminor(inode); > + struct uci_dev *udev = NULL; > + int ret; > + > + mutex_lock(&uci_drv_mutex); > + udev = idr_find(&uci_idr, minor); > + if (!udev) { > + pr_debug("uci dev: minor %d not found\n", minor); > + mutex_unlock(&uci_drv_mutex); > + return -ENODEV; > + } > + > + kref_get(&udev->ref_count); > + mutex_unlock(&uci_drv_mutex); > + > + ret = mhi_uci_dev_start_chan(udev); > + if (ret) { > + kref_put(&udev->ref_count, mhi_uci_dev_release); > + return ret; > + } > + > + filp->private_data = udev; > + > + return 0; > +} > + > +static int mhi_uci_release(struct inode *inode, struct file *file) > +{ > + struct uci_dev *udev = file->private_data; > + > + mutex_lock(&udev->lock); > + kref_put(&udev->uchan->ref_count, mhi_uci_dev_chan_release); > + mutex_unlock(&udev->lock); > + > + kref_put(&udev->ref_count, mhi_uci_dev_release); > + > + return 0; > +} > + > +static __poll_t mhi_uci_poll(struct file *file, poll_table *wait) > +{ > + struct uci_dev *udev = file->private_data; > + struct mhi_device *mhi_dev = udev->mhi_dev; > + struct device *dev = &mhi_dev->dev; > + struct uci_chan *uchan = udev->uchan; > + __poll_t mask = 0; > + > + poll_wait(file, &udev->uchan->ul_wq, wait); > + poll_wait(file, &udev->uchan->dl_wq, wait); > + > + if (!udev->enabled) { > + mask = EPOLLERR; > + goto done; > + } > + > + spin_lock_bh(&uchan->dl_pending_lock); > + if (!list_empty(&uchan->dl_pending) || uchan->cur_buf) > + mask |= EPOLLIN | EPOLLRDNORM; > + spin_unlock_bh(&uchan->dl_pending_lock); > + > + if (mhi_get_free_desc_count(mhi_dev, DMA_TO_DEVICE) > 0) > + mask |= EPOLLOUT | EPOLLWRNORM; > + > + dev_dbg(dev, "Client attempted to poll, returning mask 0x%x\n", mask); > + > +done: > + return mask; > +} > + > +static ssize_t mhi_uci_write(struct file *file, > + const char __user *buf, > + size_t count, > + loff_t *offp) > +{ > + struct uci_dev *udev = file->private_data; > + struct mhi_device *mhi_dev = udev->mhi_dev; > + struct device *dev = &mhi_dev->dev; > + struct uci_chan *uchan = udev->uchan; > + size_t bytes_xfered = 0; > + int ret, nr_desc = 0; > + > + /* if ul channel is not supported return error */ > + if (!mhi_dev->ul_chan) > + return -EOPNOTSUPP; > + > + if (!buf || !count) > + return -EINVAL; > + > + dev_dbg(dev, "%s: to xfer: %zu bytes\n", __func__, count); > + > + if (mutex_lock_interruptible(&uchan->write_lock)) > + return -EINTR; > + > + while (count) { > + size_t xfer_size; > + void *kbuf; > + enum mhi_flags flags; > + > + /* wait for free descriptors */ > + ret = wait_event_interruptible(uchan->ul_wq, > + (!udev->enabled) || > + (nr_desc = mhi_get_free_desc_count(mhi_dev, > + DMA_TO_DEVICE)) > 0); > + > + if (ret == -ERESTARTSYS) { > + dev_dbg(dev, "Interrupted by a signal in %s, exiting\n", > + __func__); > + goto err_mtx_unlock; > + } > + > + if (!udev->enabled) { > + ret = -ENODEV; > + goto err_mtx_unlock; > + } > + > + xfer_size = min_t(size_t, count, udev->mtu); > + kbuf = kmalloc(xfer_size, GFP_KERNEL); > + if (!kbuf) { > + ret = -ENOMEM; > + goto err_mtx_unlock; > + } > + > + ret = copy_from_user(kbuf, buf, xfer_size); > + if (ret) { > + kfree(kbuf); > + ret = -EFAULT; > + goto err_mtx_unlock; > + } > + > + /* if ring is full after this force EOT */ > + if (nr_desc > 1 && (count - xfer_size)) > + flags = MHI_CHAIN; > + else > + flags = MHI_EOT; > + > + ret = mhi_queue_buf(mhi_dev, DMA_TO_DEVICE, kbuf, xfer_size, > + flags); > + if (ret) { > + kfree(kbuf); > + goto err_mtx_unlock; > + } > + > + bytes_xfered += xfer_size; > + count -= xfer_size; > + buf += xfer_size; > + } > + > + mutex_unlock(&uchan->write_lock); > + dev_dbg(dev, "%s: bytes xferred: %zu\n", __func__, bytes_xfered); > + > + return bytes_xfered; > + > +err_mtx_unlock: > + mutex_unlock(&uchan->write_lock); > + > + return ret; > +} > + > +static ssize_t mhi_uci_read(struct file *file, > + char __user *buf, > + size_t count, > + loff_t *ppos) > +{ > + struct uci_dev *udev = file->private_data; > + struct mhi_device *mhi_dev = udev->mhi_dev; > + struct uci_chan *uchan = udev->uchan; > + struct device *dev = &mhi_dev->dev; > + struct uci_buf *ubuf; > + size_t rx_buf_size; > + char *ptr; > + size_t to_copy; > + int ret = 0; > + > + /* if dl channel is not supported return error */ > + if (!mhi_dev->dl_chan) > + return -EOPNOTSUPP; > + > + if (!buf) > + return -EINVAL; > + > + if (mutex_lock_interruptible(&uchan->read_lock)) > + return -EINTR; > + > + spin_lock_bh(&uchan->dl_pending_lock); > + /* No data available to read, wait */ > + if (!uchan->cur_buf && list_empty(&uchan->dl_pending)) { > + dev_dbg(dev, "No data available to read, waiting\n"); > + > + spin_unlock_bh(&uchan->dl_pending_lock); > + ret = wait_event_interruptible(uchan->dl_wq, > + (!udev->enabled || > + !list_empty(&uchan->dl_pending))); > + > + if (ret == -ERESTARTSYS) { > + dev_dbg(dev, "Interrupted by a signal in %s, exiting\n", > + __func__); > + goto err_mtx_unlock; > + } > + > + if (!udev->enabled) { > + ret = -ENODEV; > + goto err_mtx_unlock; > + } > + spin_lock_bh(&uchan->dl_pending_lock); > + } > + > + /* new read, get the next descriptor from the list */ > + if (!uchan->cur_buf) { > + ubuf = list_first_entry_or_null(&uchan->dl_pending, > + struct uci_buf, node); > + if (!ubuf) { > + ret = -EIO; > + goto err_spin_unlock; > + } > + > + list_del(&ubuf->node); > + uchan->cur_buf = ubuf; > + uchan->dl_size = ubuf->len; > + dev_dbg(dev, "Got pkt of size: %zu\n", uchan->dl_size); > + } > + spin_unlock_bh(&uchan->dl_pending_lock); > + > + ubuf = uchan->cur_buf; > + > + /* Copy the buffer to user space */ > + to_copy = min_t(size_t, count, uchan->dl_size); > + ptr = ubuf->data + (ubuf->len - uchan->dl_size); > + > + ret = copy_to_user(buf, ptr, to_copy); > + if (ret) { > + ret = -EFAULT; > + goto err_mtx_unlock; > + } > + > + dev_dbg(dev, "Copied %zu of %zu bytes\n", to_copy, uchan->dl_size); > + uchan->dl_size -= to_copy; > + > + /* we finished with this buffer, queue it back to hardware */ > + if (!uchan->dl_size) { > + uchan->cur_buf = NULL; > + > + rx_buf_size = udev->mtu - sizeof(*ubuf); > + ret = mhi_queue_buf(mhi_dev, DMA_FROM_DEVICE, ubuf->data, > + rx_buf_size, MHI_EOT); > + if (ret) { > + dev_err(dev, "Failed to recycle element: %d\n", ret); > + kfree(ubuf->data); > + goto err_mtx_unlock; > + } > + } > + mutex_unlock(&uchan->read_lock); > + > + dev_dbg(dev, "%s: Returning %zu bytes\n", __func__, to_copy); > + > + return to_copy; > + > +err_spin_unlock: > + spin_unlock_bh(&uchan->dl_pending_lock); > +err_mtx_unlock: > + mutex_unlock(&uchan->read_lock); > + return ret; > +} > + > +static const struct file_operations mhidev_fops = { > + .owner = THIS_MODULE, > + .open = mhi_uci_open, > + .release = mhi_uci_release, > + .read = mhi_uci_read, > + .write = mhi_uci_write, > + .poll = mhi_uci_poll, > +}; > + > +static void mhi_ul_xfer_cb(struct mhi_device *mhi_dev, > + struct mhi_result *mhi_result) > +{ > + struct uci_dev *udev = dev_get_drvdata(&mhi_dev->dev); > + struct uci_chan *uchan = udev->uchan; > + struct device *dev = &mhi_dev->dev; > + > + dev_dbg(dev, "%s: status: %d xfer_len: %zu\n", __func__, > + mhi_result->transaction_status, mhi_result->bytes_xferd); > + > + kfree(mhi_result->buf_addr); > + > + if (!mhi_result->transaction_status) > + wake_up(&uchan->ul_wq); > +} > + > +static void mhi_dl_xfer_cb(struct mhi_device *mhi_dev, > + struct mhi_result *mhi_result) > +{ > + struct uci_dev *udev = dev_get_drvdata(&mhi_dev->dev); > + struct uci_chan *uchan = udev->uchan; > + struct device *dev = &mhi_dev->dev; > + struct uci_buf *ubuf; > + size_t dl_buf_size = udev->mtu - sizeof(*ubuf); > + > + dev_dbg(dev, "%s: status: %d receive_len: %zu\n", __func__, > + mhi_result->transaction_status, mhi_result->bytes_xferd); > + > + if (mhi_result->transaction_status && > + mhi_result->transaction_status != -EOVERFLOW) { > + kfree(mhi_result->buf_addr); > + return; > + } > + > + ubuf = mhi_result->buf_addr + dl_buf_size; > + ubuf->data = mhi_result->buf_addr; > + ubuf->len = mhi_result->bytes_xferd; > + spin_lock_bh(&uchan->dl_pending_lock); > + list_add_tail(&ubuf->node, &uchan->dl_pending); > + spin_unlock_bh(&uchan->dl_pending_lock); > + > + wake_up(&uchan->dl_wq); > +} > + > +static int mhi_uci_probe(struct mhi_device *mhi_dev, > + const struct mhi_device_id *id) > +{ > + struct uci_dev *udev; > + struct device *dev; > + int index; > + > + udev = kzalloc(sizeof(*udev), GFP_KERNEL); > + if (!udev) > + return -ENOMEM; > + > + kref_init(&udev->ref_count); > + mutex_init(&udev->lock); > + udev->mhi_dev = mhi_dev; > + > + mutex_lock(&uci_drv_mutex); > + index = idr_alloc(&uci_idr, udev, 0, MHI_MAX_UCI_MINORS, GFP_KERNEL); > + mutex_unlock(&uci_drv_mutex); > + if (index < 0) { > + kfree(udev); > + return index; > + } > + > + udev->minor = index; > + > + udev->mtu = min_t(size_t, id->driver_data, MHI_MAX_MTU); > + dev_set_drvdata(&mhi_dev->dev, udev); > + udev->enabled = true; > + > + /* create device file node /dev/mhi_<mhi_dev_name> */ > + dev = device_create(uci_dev_class, &mhi_dev->dev, > + MKDEV(uci_dev_major, index), udev, > + MHI_DEVICE_NAME "_%s", dev_name(&mhi_dev->dev)); > + if (IS_ERR(dev)) { > + mutex_lock(&uci_drv_mutex); > + idr_remove(&uci_idr, udev->minor); > + mutex_unlock(&uci_drv_mutex); > + dev_set_drvdata(&mhi_dev->dev, NULL); > + kfree(udev); > + return PTR_ERR(dev); > + } > + > + dev_dbg(&mhi_dev->dev, "probed uci dev: %s\n", id->chan); > + > + return 0; > +}; > + > +static void mhi_uci_remove(struct mhi_device *mhi_dev) > +{ > + struct uci_dev *udev = dev_get_drvdata(&mhi_dev->dev); > + > + /* disable the node */ > + mutex_lock(&udev->lock); > + udev->enabled = false; > + > + /* delete the node to prevent new opens */ > + device_destroy(uci_dev_class, MKDEV(uci_dev_major, udev->minor)); > + > + /* return error for any blocked read or write */ > + if (udev->uchan) { > + wake_up(&udev->uchan->ul_wq); > + wake_up(&udev->uchan->dl_wq); > + } > + mutex_unlock(&udev->lock); > + > + mutex_lock(&uci_drv_mutex); > + idr_remove(&uci_idr, udev->minor); > + kref_put(&udev->ref_count, mhi_uci_dev_release); > + mutex_unlock(&uci_drv_mutex); > +} > + > +/* .driver_data stores max mtu */ > +static const struct mhi_device_id mhi_uci_match_table[] = { > + { .chan = "QMI", .driver_data = 0x1000}, > + {}, > +}; > +MODULE_DEVICE_TABLE(mhi, mhi_uci_match_table); > + > +static struct mhi_driver mhi_uci_driver = { > + .id_table = mhi_uci_match_table, > + .remove = mhi_uci_remove, > + .probe = mhi_uci_probe, > + .ul_xfer_cb = mhi_ul_xfer_cb, > + .dl_xfer_cb = mhi_dl_xfer_cb, > + .driver = { > + .name = MHI_UCI_DRIVER_NAME, > + }, > +}; > + > +static int __init mhi_uci_init(void) > +{ > + int ret; > + > + ret = register_chrdev(0, MHI_UCI_DRIVER_NAME, &mhidev_fops); > + if (ret < 0) > + return ret; > + > + uci_dev_major = ret; > + uci_dev_class = class_create(THIS_MODULE, MHI_UCI_DRIVER_NAME); > + if (IS_ERR(uci_dev_class)) { > + unregister_chrdev(uci_dev_major, MHI_UCI_DRIVER_NAME); > + return PTR_ERR(uci_dev_class); > + } > + > + ret = mhi_driver_register(&mhi_uci_driver); > + if (ret) { > + class_destroy(uci_dev_class); > + unregister_chrdev(uci_dev_major, MHI_UCI_DRIVER_NAME); > + } > + > + return ret; > +} > + > +static void __exit mhi_uci_exit(void) > +{ > + mhi_driver_unregister(&mhi_uci_driver); > + class_destroy(uci_dev_class); > + unregister_chrdev(uci_dev_major, MHI_UCI_DRIVER_NAME); > + idr_destroy(&uci_idr); > +} > + > +module_init(mhi_uci_init); > +module_exit(mhi_uci_exit); > +MODULE_LICENSE("GPL v2"); > +MODULE_DESCRIPTION("MHI UCI Driver"); > -- > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, > a Linux Foundation Collaborative Project >
Hi Mani, On 11/27/20 10:11 PM, Manivannan Sadhasivam wrote: > Hi Hemant, > > On Fri, Nov 27, 2020 at 07:26:06PM -0800, Hemant Kumar wrote: >> This MHI client driver allows userspace clients to transfer >> raw data between MHI device and host using standard file operations. >> Driver instantiates UCI device object which is associated to device >> file node. UCI device object instantiates UCI channel object when device >> file node is opened. UCI channel object is used to manage MHI channels >> by calling MHI core APIs for read and write operations. MHI channels >> are started as part of device open(). MHI channels remain in start >> state until last release() is called on UCI device file node. Device >> file node is created with format >> >> /dev/mhi_<mhi_device_name> >> >> Currently it supports QMI channel. >> > > Thanks for the update. This patch looks good to me. But as I'm going to > apply Loic's "bus: mhi: core: Indexed MHI controller name" patch, you > need to update the documentation accordingly. This is what i added in documentation on v13 Device file node is created with format:- /dev/mhi_<mhi_device_name> mhi_device_name includes mhi controller name and the name of the MHI channel being used by MHI client in userspace to send or receive data using MHI protocol. Loic's patch is going to update the controller name as indexed controller name, which goes fine with or without his change going first. For example: With Loic's change name of device node would be /dev/mhi_mhi0_QMI Without Loic's change it would be /dev/mhi_0000:00:01.2_QMI Please let me know if i am missing something. Thanks, Hemant > >> Signed-off-by: Hemant Kumar <hemantk@codeaurora.org> > > Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org> > > Thanks, > Mani > [..]
On Fri, 27 Nov 2020 19:26:02 -0800 Hemant Kumar wrote: > This patch series adds support for UCI driver. UCI driver enables userspace > clients to communicate to external MHI devices like modem and WLAN. UCI driver > probe creates standard character device file nodes for userspace clients to > perform open, read, write, poll and release file operations. These file > operations call MHI core layer APIs to perform data transfer using MHI bus > to communicate with MHI device. Patch is tested using arm64 based platform. Wait, I thought this was for modems. Why do WLAN devices need to communicate with user space?
On 12/1/2020 12:29 PM, Jakub Kicinski wrote: > On Fri, 27 Nov 2020 19:26:02 -0800 Hemant Kumar wrote: >> This patch series adds support for UCI driver. UCI driver enables userspace >> clients to communicate to external MHI devices like modem and WLAN. UCI driver >> probe creates standard character device file nodes for userspace clients to >> perform open, read, write, poll and release file operations. These file >> operations call MHI core layer APIs to perform data transfer using MHI bus >> to communicate with MHI device. Patch is tested using arm64 based platform. > > Wait, I thought this was for modems. > > Why do WLAN devices need to communicate with user space? > Why does it matter what type of device it is? Are modems somehow unique in that they are the only type of device that userspace is allowed to interact with? However, I'll bite. Once such usecase would be QMI. QMI is a generic messaging protocol, and is not strictly limited to the unique operations of a modem. Another usecase would be Sahara - a custom file transfer protocol used for uploading firmware images, and downloading crashdumps. Off the top of my head, this driver is useful for modems, wlan, and AI accelerators.
On Tue, 1 Dec 2020 12:40:50 -0700 Jeffrey Hugo wrote: > On 12/1/2020 12:29 PM, Jakub Kicinski wrote: > > On Fri, 27 Nov 2020 19:26:02 -0800 Hemant Kumar wrote: > >> This patch series adds support for UCI driver. UCI driver enables userspace > >> clients to communicate to external MHI devices like modem and WLAN. UCI driver > >> probe creates standard character device file nodes for userspace clients to > >> perform open, read, write, poll and release file operations. These file > >> operations call MHI core layer APIs to perform data transfer using MHI bus > >> to communicate with MHI device. Patch is tested using arm64 based platform. > > > > Wait, I thought this was for modems. > > > > Why do WLAN devices need to communicate with user space? > > > > Why does it matter what type of device it is? Are modems somehow unique > in that they are the only type of device that userspace is allowed to > interact with? Yes modems are traditionally highly weird and require some serial device dance I don't even know about. We have proper interfaces in Linux for configuring WiFi which work across vendors. Having char device access to WiFi would be a step back. > However, I'll bite. Once such usecase would be QMI. QMI is a generic > messaging protocol, and is not strictly limited to the unique operations > of a modem. > > Another usecase would be Sahara - a custom file transfer protocol used > for uploading firmware images, and downloading crashdumps. Thanks, I was asking for use cases, not which proprietary vendor protocol you can implement over it. None of the use cases you mention here should require a direct FW - user space backdoor for WLAN. > Off the top of my head, this driver is useful for modems, wlan, and AI > accelerators. And other Qualcomm products are available as well :/ Kernel is supposed to create abstract interfaces for user space to utilize. I will never understand why kernel is expected to be in business of shipping this sort of vendor backdoors :/
On 12/1/2020 1:03 PM, Jakub Kicinski wrote: > On Tue, 1 Dec 2020 12:40:50 -0700 Jeffrey Hugo wrote: >> On 12/1/2020 12:29 PM, Jakub Kicinski wrote: >>> On Fri, 27 Nov 2020 19:26:02 -0800 Hemant Kumar wrote: >>>> This patch series adds support for UCI driver. UCI driver enables userspace >>>> clients to communicate to external MHI devices like modem and WLAN. UCI driver >>>> probe creates standard character device file nodes for userspace clients to >>>> perform open, read, write, poll and release file operations. These file >>>> operations call MHI core layer APIs to perform data transfer using MHI bus >>>> to communicate with MHI device. Patch is tested using arm64 based platform. >>> >>> Wait, I thought this was for modems. >>> >>> Why do WLAN devices need to communicate with user space? >>> >> >> Why does it matter what type of device it is? Are modems somehow unique >> in that they are the only type of device that userspace is allowed to >> interact with? > > Yes modems are traditionally highly weird and require some serial > device dance I don't even know about. > > We have proper interfaces in Linux for configuring WiFi which work > across vendors. Having char device access to WiFi would be a step > back. So a WLAN device is only ever allowed to do Wi-Fi? It can't also have GPS functionality for example? > >> However, I'll bite. Once such usecase would be QMI. QMI is a generic >> messaging protocol, and is not strictly limited to the unique operations >> of a modem. >> >> Another usecase would be Sahara - a custom file transfer protocol used >> for uploading firmware images, and downloading crashdumps. > > Thanks, I was asking for use cases, not which proprietary vendor > protocol you can implement over it. > > None of the use cases you mention here should require a direct FW - > user space backdoor for WLAN. Uploading runtime firmware, with variations based on the runtime mode. Flashing the onboard flash based on cryptographic keys. Accessing configuration data. Accessing device logs. Configuring device logs. Synchronizing the device time reference to Linux local or remote time sources. Enabling debugging/performance hardware. Getting software diagnostic events. Configuring redundancy hardware per workload. Uploading new cryptographic keys. Invalidating cryptographic keys. Uploading factory test data and running factory tests. Need more?
On Tue, 1 Dec 2020 13:48:36 -0700 Jeffrey Hugo wrote: > On 12/1/2020 1:03 PM, Jakub Kicinski wrote: > > On Tue, 1 Dec 2020 12:40:50 -0700 Jeffrey Hugo wrote: > >> On 12/1/2020 12:29 PM, Jakub Kicinski wrote: > >>> On Fri, 27 Nov 2020 19:26:02 -0800 Hemant Kumar wrote: > >>>> This patch series adds support for UCI driver. UCI driver enables userspace > >>>> clients to communicate to external MHI devices like modem and WLAN. UCI driver > >>>> probe creates standard character device file nodes for userspace clients to > >>>> perform open, read, write, poll and release file operations. These file > >>>> operations call MHI core layer APIs to perform data transfer using MHI bus > >>>> to communicate with MHI device. Patch is tested using arm64 based platform. > >>> > >>> Wait, I thought this was for modems. > >>> > >>> Why do WLAN devices need to communicate with user space? > >>> > >> > >> Why does it matter what type of device it is? Are modems somehow unique > >> in that they are the only type of device that userspace is allowed to > >> interact with? > > > > Yes modems are traditionally highly weird and require some serial > > device dance I don't even know about. > > > > We have proper interfaces in Linux for configuring WiFi which work > > across vendors. Having char device access to WiFi would be a step > > back. > > So a WLAN device is only ever allowed to do Wi-Fi? It can't also have > GPS functionality for example? No, but it's also not true that the only way to implement GPS is by opening a full on command/packet interface between fat proprietary firmware and custom user space (which may or may not be proprietary as well). > >> However, I'll bite. Once such usecase would be QMI. QMI is a generic > >> messaging protocol, and is not strictly limited to the unique operations > >> of a modem. > >> > >> Another usecase would be Sahara - a custom file transfer protocol used > >> for uploading firmware images, and downloading crashdumps. > > > > Thanks, I was asking for use cases, not which proprietary vendor > > protocol you can implement over it. > > > > None of the use cases you mention here should require a direct FW - > > user space backdoor for WLAN. > > Uploading runtime firmware, with variations based on the runtime mode. > Flashing the onboard flash based on cryptographic keys. Accessing > configuration data. Accessing device logs. Configuring device logs. > Synchronizing the device time reference to Linux local or remote time > sources. Enabling debugging/performance hardware. Getting software > diagnostic events. Configuring redundancy hardware per workload. > Uploading new cryptographic keys. Invalidating cryptographic keys. > Uploading factory test data and running factory tests. > > Need more? This conversation is going nowhere. Are you trying to say that creating a common Linux API for those features is impossible and each vendor should be allowed to add their own proprietary way? This has been proven incorrect again and again, and Wi-Fi is a good example. You can do whatever you want for GPS etc. but don't come nowhere near networking with this attitude please.
On Tue, Dec 01, 2020 at 12:03:02PM -0800, Jakub Kicinski wrote: > On Tue, 1 Dec 2020 12:40:50 -0700 Jeffrey Hugo wrote: > > On 12/1/2020 12:29 PM, Jakub Kicinski wrote: > > > On Fri, 27 Nov 2020 19:26:02 -0800 Hemant Kumar wrote: > > >> This patch series adds support for UCI driver. UCI driver enables userspace > > >> clients to communicate to external MHI devices like modem and WLAN. UCI driver > > >> probe creates standard character device file nodes for userspace clients to > > >> perform open, read, write, poll and release file operations. These file > > >> operations call MHI core layer APIs to perform data transfer using MHI bus > > >> to communicate with MHI device. Patch is tested using arm64 based platform. > > > > > > Wait, I thought this was for modems. > > > > > > Why do WLAN devices need to communicate with user space? > > > > > > > Why does it matter what type of device it is? Are modems somehow unique > > in that they are the only type of device that userspace is allowed to > > interact with? > > Yes modems are traditionally highly weird and require some serial > device dance I don't even know about. > > We have proper interfaces in Linux for configuring WiFi which work > across vendors. Having char device access to WiFi would be a step > back. > This is not for configuring the WiFi. This driver is mostly used for modems and the AI accelerator Jeff is working on. But there might be a usecase for WLAN devices as well to collect crash dumps and download fw (typical vendor ways) but having those features are add-ons IMO. So I think we should not be blocked by those usecases. Thanks, Mani
On Tue 01 Dec 13:29 CST 2020, Jakub Kicinski wrote: > On Fri, 27 Nov 2020 19:26:02 -0800 Hemant Kumar wrote: > > This patch series adds support for UCI driver. UCI driver enables userspace > > clients to communicate to external MHI devices like modem and WLAN. UCI driver > > probe creates standard character device file nodes for userspace clients to > > perform open, read, write, poll and release file operations. These file > > operations call MHI core layer APIs to perform data transfer using MHI bus > > to communicate with MHI device. Patch is tested using arm64 based platform. > > Wait, I thought this was for modems. > No, this allows exposing particular channels from any type of MHI devices. For modems there is a legacy control path that uses UCI. But data traffic, (non-legacy) modem control signals and e.g the bearer of GPS data uses in-kernel drivers that are already in place. > Why do WLAN devices need to communicate with user space? They normally don't, all WLAN operations are dealt with within the kernel. The use case that comes to mind for UCI when it comes to WiFi products is to avoid implementing the Qualcomm debug (diag) protocol in the kernel. As such I think saying that it can be used to communicate with modem or WLAN devices is misleading. Because while it could be done, it is only used for dealing with optional side-band services on such products - not the actual WiFi and modem functionality. Regards, Bjorn
On 12/1/2020 7:55 PM, Jakub Kicinski wrote: > On Tue, 1 Dec 2020 13:48:36 -0700 Jeffrey Hugo wrote: >> On 12/1/2020 1:03 PM, Jakub Kicinski wrote: >>> On Tue, 1 Dec 2020 12:40:50 -0700 Jeffrey Hugo wrote: >>>> On 12/1/2020 12:29 PM, Jakub Kicinski wrote: >>>>> On Fri, 27 Nov 2020 19:26:02 -0800 Hemant Kumar wrote: >>>>>> This patch series adds support for UCI driver. UCI driver enables userspace >>>>>> clients to communicate to external MHI devices like modem and WLAN. UCI driver >>>>>> probe creates standard character device file nodes for userspace clients to >>>>>> perform open, read, write, poll and release file operations. These file >>>>>> operations call MHI core layer APIs to perform data transfer using MHI bus >>>>>> to communicate with MHI device. Patch is tested using arm64 based platform. >>>>> >>>>> Wait, I thought this was for modems. >>>>> >>>>> Why do WLAN devices need to communicate with user space? >>>>> >>>> >>>> Why does it matter what type of device it is? Are modems somehow unique >>>> in that they are the only type of device that userspace is allowed to >>>> interact with? >>> >>> Yes modems are traditionally highly weird and require some serial >>> device dance I don't even know about. >>> >>> We have proper interfaces in Linux for configuring WiFi which work >>> across vendors. Having char device access to WiFi would be a step >>> back. >> >> So a WLAN device is only ever allowed to do Wi-Fi? It can't also have >> GPS functionality for example? > > No, but it's also not true that the only way to implement GPS is by > opening a full on command/packet interface between fat proprietary > firmware and custom user space (which may or may not be proprietary > as well). Funny, that exactly what the GPS "API" in the kernel is, although a bit limited to the specifics on the standardized GPS "sentences" and not covering implementation specific configuration. > >>>> However, I'll bite. Once such usecase would be QMI. QMI is a generic >>>> messaging protocol, and is not strictly limited to the unique operations >>>> of a modem. >>>> >>>> Another usecase would be Sahara - a custom file transfer protocol used >>>> for uploading firmware images, and downloading crashdumps. >>> >>> Thanks, I was asking for use cases, not which proprietary vendor >>> protocol you can implement over it. >>> >>> None of the use cases you mention here should require a direct FW - >>> user space backdoor for WLAN. >> >> Uploading runtime firmware, with variations based on the runtime mode. >> Flashing the onboard flash based on cryptographic keys. Accessing >> configuration data. Accessing device logs. Configuring device logs. >> Synchronizing the device time reference to Linux local or remote time >> sources. Enabling debugging/performance hardware. Getting software >> diagnostic events. Configuring redundancy hardware per workload. >> Uploading new cryptographic keys. Invalidating cryptographic keys. >> Uploading factory test data and running factory tests. >> >> Need more? > > This conversation is going nowhere. Are you trying to say that creating > a common Linux API for those features is impossible and each vendor > should be allowed to add their own proprietary way? > > This has been proven incorrect again and again, and Wi-Fi is a good > example. > > You can do whatever you want for GPS etc. but don't come nowhere near > networking with this attitude please. > No I'm saying (and Bjorn/Mani by the looks of things), that there is commonality in the core features - IP traffic, Wi-Fi, etc but then there are vendor specific things which are either things you don't actually want in the kernel, don't want the kernel doing, or have little commonality between vendors such that attempting to unify them gains you little to nothing. Over in the networking space, I can see where standardization is plenty useful. I can't speak for other vendors, but a "modem" or a "wlan" device from Qualcomm is not something that just provides one service. They tend to provide dozens of different functionalities, some of those are "standardized" like wi-fi where common wi-fi interfaces are used. Others are unique to Qualcomm. The point is "wlan device" is a superset of "wi-fi". You seem to be equating them to be the same in a "shoot first, ask questions later" manner. This series provides a way for userspace to talk to remote MHI "widgets" for usecases not covered elsewhere. Those "widgets" just happen to commonly provide modem/wlan services, but ones that don't are not excluded. Regarding not coming near networking, I'd like to remind you it was you that decided to come over here to the non-networking area and try to make this about networking.
On Tue, Dec 01, 2020 at 09:59:53PM -0700, Jeffrey Hugo wrote: > On 12/1/2020 7:55 PM, Jakub Kicinski wrote: > > On Tue, 1 Dec 2020 13:48:36 -0700 Jeffrey Hugo wrote: > > > On 12/1/2020 1:03 PM, Jakub Kicinski wrote: > > > > On Tue, 1 Dec 2020 12:40:50 -0700 Jeffrey Hugo wrote: > > > > > On 12/1/2020 12:29 PM, Jakub Kicinski wrote: > > > > > > On Fri, 27 Nov 2020 19:26:02 -0800 Hemant Kumar wrote: > > > > > > > This patch series adds support for UCI driver. UCI driver enables userspace > > > > > > > clients to communicate to external MHI devices like modem and WLAN. UCI driver > > > > > > > probe creates standard character device file nodes for userspace clients to > > > > > > > perform open, read, write, poll and release file operations. These file > > > > > > > operations call MHI core layer APIs to perform data transfer using MHI bus > > > > > > > to communicate with MHI device. Patch is tested using arm64 based platform. > > > > > > > > > > > > Wait, I thought this was for modems. > > > > > > > > > > > > Why do WLAN devices need to communicate with user space? > > > > > > > > > > Why does it matter what type of device it is? Are modems somehow unique > > > > > in that they are the only type of device that userspace is allowed to > > > > > interact with? > > > > > > > > Yes modems are traditionally highly weird and require some serial > > > > device dance I don't even know about. > > > > > > > > We have proper interfaces in Linux for configuring WiFi which work > > > > across vendors. Having char device access to WiFi would be a step > > > > back. > > > > > > So a WLAN device is only ever allowed to do Wi-Fi? It can't also have > > > GPS functionality for example? > > > > No, but it's also not true that the only way to implement GPS is by > > opening a full on command/packet interface between fat proprietary > > firmware and custom user space (which may or may not be proprietary > > as well). > > Funny, that exactly what the GPS "API" in the kernel is, although a bit > limited to the specifics on the standardized GPS "sentences" and not > covering implementation specific configuration. > > > > > > > > However, I'll bite. Once such usecase would be QMI. QMI is a generic > > > > > messaging protocol, and is not strictly limited to the unique operations > > > > > of a modem. > > > > > > > > > > Another usecase would be Sahara - a custom file transfer protocol used > > > > > for uploading firmware images, and downloading crashdumps. > > > > > > > > Thanks, I was asking for use cases, not which proprietary vendor > > > > protocol you can implement over it. > > > > > > > > None of the use cases you mention here should require a direct FW - > > > > user space backdoor for WLAN. > > > > > > Uploading runtime firmware, with variations based on the runtime mode. > > > Flashing the onboard flash based on cryptographic keys. Accessing > > > configuration data. Accessing device logs. Configuring device logs. > > > Synchronizing the device time reference to Linux local or remote time > > > sources. Enabling debugging/performance hardware. Getting software > > > diagnostic events. Configuring redundancy hardware per workload. > > > Uploading new cryptographic keys. Invalidating cryptographic keys. > > > Uploading factory test data and running factory tests. > > > > > > Need more? > > > > This conversation is going nowhere. Are you trying to say that creating > > a common Linux API for those features is impossible and each vendor > > should be allowed to add their own proprietary way? > > > > This has been proven incorrect again and again, and Wi-Fi is a good > > example. > > > > You can do whatever you want for GPS etc. but don't come nowhere near > > networking with this attitude please. > > > > No I'm saying (and Bjorn/Mani by the looks of things), that there is > commonality in the core features - IP traffic, Wi-Fi, etc but then there are > vendor specific things which are either things you don't actually want in > the kernel, don't want the kernel doing, or have little commonality between > vendors such that attempting to unify them gains you little to nothing. > > Over in the networking space, I can see where standardization is plenty > useful. > > I can't speak for other vendors, but a "modem" or a "wlan" device from > Qualcomm is not something that just provides one service. They tend to > provide dozens of different functionalities, some of those are > "standardized" like wi-fi where common wi-fi interfaces are used. Others are > unique to Qualcomm. > > The point is "wlan device" is a superset of "wi-fi". You seem to be > equating them to be the same in a "shoot first, ask questions later" manner. > > This series provides a way for userspace to talk to remote MHI "widgets" for > usecases not covered elsewhere. Those "widgets" just happen to commonly > provide modem/wlan services, but ones that don't are not excluded. > > Regarding not coming near networking, I'd like to remind you it was you that > decided to come over here to the non-networking area and try to make this > about networking. Like it or not, but Jakub is absolutely right with his claim that providing user-visible interfaces without any standardization is proven as wrong. Thanks > > -- > Jeffrey Hugo > Qualcomm Technologies, Inc. is a member of the > Code Aurora Forum, a Linux Foundation Collaborative Project.
On Sun, Dec 06, 2020 at 10:33:02AM +0200, Leon Romanovsky wrote: > On Tue, Dec 01, 2020 at 09:59:53PM -0700, Jeffrey Hugo wrote: > > On 12/1/2020 7:55 PM, Jakub Kicinski wrote: > > > On Tue, 1 Dec 2020 13:48:36 -0700 Jeffrey Hugo wrote: > > > > On 12/1/2020 1:03 PM, Jakub Kicinski wrote: > > > > > On Tue, 1 Dec 2020 12:40:50 -0700 Jeffrey Hugo wrote: > > > > > > On 12/1/2020 12:29 PM, Jakub Kicinski wrote: > > > > > > > On Fri, 27 Nov 2020 19:26:02 -0800 Hemant Kumar wrote: > > > > > > > > This patch series adds support for UCI driver. UCI driver enables userspace > > > > > > > > clients to communicate to external MHI devices like modem and WLAN. UCI driver > > > > > > > > probe creates standard character device file nodes for userspace clients to > > > > > > > > perform open, read, write, poll and release file operations. These file > > > > > > > > operations call MHI core layer APIs to perform data transfer using MHI bus > > > > > > > > to communicate with MHI device. Patch is tested using arm64 based platform. > > > > > > > > > > > > > > Wait, I thought this was for modems. > > > > > > > [...] > Like it or not, but Jakub is absolutely right with his claim that > providing user-visible interfaces without any standardization is proven > as wrong. > Everybody agrees with standardizing things but the problem is, the standardization will only happen when more than one person implements the same functionality. The primary discussion is around the usage of chardev nodes for WLAN but we made it clear that WLAN doesn't need this chardev node for working at all. I agree that the commit message is a bit misleading and I hope that Hemant will fix it in next revision. Thanks, Mani > Thanks > > > > > -- > > Jeffrey Hugo > > Qualcomm Technologies, Inc. is a member of the > > Code Aurora Forum, a Linux Foundation Collaborative Project.
On Tue, Dec 08, 2020 at 10:29:27PM +0530, Manivannan Sadhasivam wrote: > On Sun, Dec 06, 2020 at 10:33:02AM +0200, Leon Romanovsky wrote: > > On Tue, Dec 01, 2020 at 09:59:53PM -0700, Jeffrey Hugo wrote: > > > On 12/1/2020 7:55 PM, Jakub Kicinski wrote: > > > > On Tue, 1 Dec 2020 13:48:36 -0700 Jeffrey Hugo wrote: > > > > > On 12/1/2020 1:03 PM, Jakub Kicinski wrote: > > > > > > On Tue, 1 Dec 2020 12:40:50 -0700 Jeffrey Hugo wrote: > > > > > > > On 12/1/2020 12:29 PM, Jakub Kicinski wrote: > > > > > > > > On Fri, 27 Nov 2020 19:26:02 -0800 Hemant Kumar wrote: > > > > > > > > > This patch series adds support for UCI driver. UCI driver enables userspace > > > > > > > > > clients to communicate to external MHI devices like modem and WLAN. UCI driver > > > > > > > > > probe creates standard character device file nodes for userspace clients to > > > > > > > > > perform open, read, write, poll and release file operations. These file > > > > > > > > > operations call MHI core layer APIs to perform data transfer using MHI bus > > > > > > > > > to communicate with MHI device. Patch is tested using arm64 based platform. > > > > > > > > > > > > > > > > Wait, I thought this was for modems. > > > > > > > > > > [...] > > > Like it or not, but Jakub is absolutely right with his claim that > > providing user-visible interfaces without any standardization is proven > > as wrong. > > > > Everybody agrees with standardizing things but the problem is, the > standardization will only happen when more than one person implements the > same functionality. From my experience in RDMA and netdev, I can't agree with both of your statements. There are a lot of people who see standardization as a bad thing. Also we are pushing even one person to make user visible interfaces right from the beginning without relation to how wide it will be adopted later. Thanks