| Message ID | 20250410-uio-dma-v1-2-6468ace2c786@bootlin.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | uio/dma-buf: Give UIO users access to DMA addresses. | expand |
Hi Bastien, Le jeudi 10 avril 2025 à 16:53 +0200, Bastien Curutchet a écrit : > There is no way to transmit the DMA address of a buffer to userspace. > Some UIO users need this to handle DMA from userspace. To me this API is against all safe practice we've been pushing forward and has no place in DMA_BUF API. If this is fine for the UIO subsystem to pass around physicial addresses, then make this part of the UIO device ioctl. regards, Nicolas > > Add a new dma_buf_ops operation that returns the DMA address. > Add a new ioctl to transmit this DMA address to userspace. > > Signed-off-by: Bastien Curutchet <bastien.curutchet@bootlin.com> > --- > drivers/dma-buf/dma-buf.c | 21 +++++++++++++++++++++ > include/linux/dma-buf.h | 1 + > include/uapi/linux/dma-buf.h | 1 + > 3 files changed, 23 insertions(+) > > diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c > index > 398418bd9731ad7a3a1f12eaea6a155fa77a22fe..cbbb518981e54e50f479c3d1fcf > 6da6971f639c1 100644 > --- a/drivers/dma-buf/dma-buf.c > +++ b/drivers/dma-buf/dma-buf.c > @@ -454,6 +454,24 @@ static long dma_buf_import_sync_file(struct > dma_buf *dmabuf, > } > #endif > > +static int dma_buf_get_dma_addr(struct dma_buf *dmabuf, u64 __user > *arg) > +{ > + u64 addr; > + int ret; > + > + if (!dmabuf->ops->get_dma_addr) > + return -EINVAL; > + > + ret = dmabuf->ops->get_dma_addr(dmabuf, &addr); > + if (ret) > + return ret; > + > + if (copy_to_user(arg, &addr, sizeof(u64))) > + return -EFAULT; > + > + return 0; > +} > + > static long dma_buf_ioctl(struct file *file, > unsigned int cmd, unsigned long arg) > { > @@ -504,6 +522,9 @@ static long dma_buf_ioctl(struct file *file, > return dma_buf_import_sync_file(dmabuf, (const void > __user *)arg); > #endif > > + case DMA_BUF_IOCTL_GET_DMA_ADDR: > + return dma_buf_get_dma_addr(dmabuf, (u64 __user > *)arg); > + > default: > return -ENOTTY; > } > diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h > index > 36216d28d8bdc01a9c9c47e27c392413f7f6c5fb..ed4bf15d3ce82e7a86323fff459 > 699a9bc8baa3b 100644 > --- a/include/linux/dma-buf.h > +++ b/include/linux/dma-buf.h > @@ -285,6 +285,7 @@ struct dma_buf_ops { > > int (*vmap)(struct dma_buf *dmabuf, struct iosys_map *map); > void (*vunmap)(struct dma_buf *dmabuf, struct iosys_map > *map); > + int (*get_dma_addr)(struct dma_buf *dmabuf, u64 *addr); > }; > > /** > diff --git a/include/uapi/linux/dma-buf.h b/include/uapi/linux/dma- > buf.h > index > 5a6fda66d9adf01438619e7e67fa69f0fec2d88d..f3aba46942042de6a2e3a4cca3e > b3f87175e29c9 100644 > --- a/include/uapi/linux/dma-buf.h > +++ b/include/uapi/linux/dma-buf.h > @@ -178,5 +178,6 @@ struct dma_buf_import_sync_file { > #define DMA_BUF_SET_NAME_B _IOW(DMA_BUF_BASE, 1, __u64) > #define DMA_BUF_IOCTL_EXPORT_SYNC_FILE _IOWR(DMA_BUF_BASE, 2, > struct dma_buf_export_sync_file) > #define DMA_BUF_IOCTL_IMPORT_SYNC_FILE _IOW(DMA_BUF_BASE, 3, struct > dma_buf_import_sync_file) > +#define DMA_BUF_IOCTL_GET_DMA_ADDR _IOR(DMA_BUF_BASE, 4, __u64 > *) > > #endif
diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c index 398418bd9731ad7a3a1f12eaea6a155fa77a22fe..cbbb518981e54e50f479c3d1fcf6da6971f639c1 100644 --- a/drivers/dma-buf/dma-buf.c +++ b/drivers/dma-buf/dma-buf.c @@ -454,6 +454,24 @@ static long dma_buf_import_sync_file(struct dma_buf *dmabuf, } #endif +static int dma_buf_get_dma_addr(struct dma_buf *dmabuf, u64 __user *arg) +{ + u64 addr; + int ret; + + if (!dmabuf->ops->get_dma_addr) + return -EINVAL; + + ret = dmabuf->ops->get_dma_addr(dmabuf, &addr); + if (ret) + return ret; + + if (copy_to_user(arg, &addr, sizeof(u64))) + return -EFAULT; + + return 0; +} + static long dma_buf_ioctl(struct file *file, unsigned int cmd, unsigned long arg) { @@ -504,6 +522,9 @@ static long dma_buf_ioctl(struct file *file, return dma_buf_import_sync_file(dmabuf, (const void __user *)arg); #endif + case DMA_BUF_IOCTL_GET_DMA_ADDR: + return dma_buf_get_dma_addr(dmabuf, (u64 __user *)arg); + default: return -ENOTTY; } diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h index 36216d28d8bdc01a9c9c47e27c392413f7f6c5fb..ed4bf15d3ce82e7a86323fff459699a9bc8baa3b 100644 --- a/include/linux/dma-buf.h +++ b/include/linux/dma-buf.h @@ -285,6 +285,7 @@ struct dma_buf_ops { int (*vmap)(struct dma_buf *dmabuf, struct iosys_map *map); void (*vunmap)(struct dma_buf *dmabuf, struct iosys_map *map); + int (*get_dma_addr)(struct dma_buf *dmabuf, u64 *addr); }; /** diff --git a/include/uapi/linux/dma-buf.h b/include/uapi/linux/dma-buf.h index 5a6fda66d9adf01438619e7e67fa69f0fec2d88d..f3aba46942042de6a2e3a4cca3eb3f87175e29c9 100644 --- a/include/uapi/linux/dma-buf.h +++ b/include/uapi/linux/dma-buf.h @@ -178,5 +178,6 @@ struct dma_buf_import_sync_file { #define DMA_BUF_SET_NAME_B _IOW(DMA_BUF_BASE, 1, __u64) #define DMA_BUF_IOCTL_EXPORT_SYNC_FILE _IOWR(DMA_BUF_BASE, 2, struct dma_buf_export_sync_file) #define DMA_BUF_IOCTL_IMPORT_SYNC_FILE _IOW(DMA_BUF_BASE, 3, struct dma_buf_import_sync_file) +#define DMA_BUF_IOCTL_GET_DMA_ADDR _IOR(DMA_BUF_BASE, 4, __u64 *) #endif
There is no way to transmit the DMA address of a buffer to userspace. Some UIO users need this to handle DMA from userspace. Add a new dma_buf_ops operation that returns the DMA address. Add a new ioctl to transmit this DMA address to userspace. Signed-off-by: Bastien Curutchet <bastien.curutchet@bootlin.com> --- drivers/dma-buf/dma-buf.c | 21 +++++++++++++++++++++ include/linux/dma-buf.h | 1 + include/uapi/linux/dma-buf.h | 1 + 3 files changed, 23 insertions(+)