| Message ID | 20210224092304.29932-1-tzimmermann@suse.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v4] drm: Use USB controller's DMA mask when importing dmabufs | expand |
On Wed, Feb 24, 2021 at 10:23:04AM +0100, Thomas Zimmermann wrote: > USB devices cannot perform DMA and hence have no dma_mask set in their > device structure. Therefore importing dmabuf into a USB-based driver > fails, which breaks joining and mirroring of display in X11. > > For USB devices, pick the associated USB controller as attachment device. > This allows the DRM import helpers to perform the DMA setup. If the DMA > controller does not support DMA transfers, we're out of luck and cannot > import. Our current USB-based DRM drivers don't use DMA, so the actual > DMA device is not important. > > Drivers should use DRM_GEM_SHMEM_DROVER_OPS_USB to initialize their > instance of struct drm_driver. > > Tested by joining/mirroring displays of udl and radeon un der Gnome/X11. > > v4: > * implement workaround with USB helper functions (Greg) > * use struct usb_device->bus->sysdev as DMA device (Takashi) > v3: > * drop gem_create_object > * use DMA mask of USB controller, if any (Daniel, Christian, Noralf) > v2: > * move fix to importer side (Christian, Daniel) > * update SHMEM and CMA helpers for new PRIME callbacks > > Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de> > Fixes: 6eb0233ec2d0 ("usb: don't inherity DMA properties for USB devices") > Cc: Christoph Hellwig <hch@lst.de> > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > Cc: <stable@vger.kernel.org> # v5.10+ > --- > +struct drm_gem_object *drm_gem_prime_import_usb(struct drm_device *dev, > + struct dma_buf *dma_buf) > +{ > + struct usb_device *udev; > + struct device *dmadev; > + struct drm_gem_object *obj; > + > + if (!dev_is_usb(dev->dev)) > + return ERR_PTR(-ENODEV); > + udev = interface_to_usbdev(to_usb_interface(dev->dev)); > + > + dmadev = usb_get_dma_device(udev); You can do it this way if you want, but I think usb_get_dma_device would be easier to use if its argument was a pointer to struct usb_interface or (even better) a pointer to a usb_interface's embedded struct device. Then you wouldn't need to compute udev, and the same would be true for other callers. Alan Stern
Hi Am 24.02.21 um 16:21 schrieb Alan Stern: > On Wed, Feb 24, 2021 at 10:23:04AM +0100, Thomas Zimmermann wrote: >> USB devices cannot perform DMA and hence have no dma_mask set in their >> device structure. Therefore importing dmabuf into a USB-based driver >> fails, which breaks joining and mirroring of display in X11. >> >> For USB devices, pick the associated USB controller as attachment device. >> This allows the DRM import helpers to perform the DMA setup. If the DMA >> controller does not support DMA transfers, we're out of luck and cannot >> import. Our current USB-based DRM drivers don't use DMA, so the actual >> DMA device is not important. >> >> Drivers should use DRM_GEM_SHMEM_DROVER_OPS_USB to initialize their >> instance of struct drm_driver. >> >> Tested by joining/mirroring displays of udl and radeon un der Gnome/X11. >> >> v4: >> * implement workaround with USB helper functions (Greg) >> * use struct usb_device->bus->sysdev as DMA device (Takashi) >> v3: >> * drop gem_create_object >> * use DMA mask of USB controller, if any (Daniel, Christian, Noralf) >> v2: >> * move fix to importer side (Christian, Daniel) >> * update SHMEM and CMA helpers for new PRIME callbacks >> >> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de> >> Fixes: 6eb0233ec2d0 ("usb: don't inherity DMA properties for USB devices") >> Cc: Christoph Hellwig <hch@lst.de> >> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> >> Cc: <stable@vger.kernel.org> # v5.10+ >> --- > >> +struct drm_gem_object *drm_gem_prime_import_usb(struct drm_device *dev, >> + struct dma_buf *dma_buf) >> +{ >> + struct usb_device *udev; >> + struct device *dmadev; >> + struct drm_gem_object *obj; >> + >> + if (!dev_is_usb(dev->dev)) >> + return ERR_PTR(-ENODEV); >> + udev = interface_to_usbdev(to_usb_interface(dev->dev)); >> + >> + dmadev = usb_get_dma_device(udev); > > You can do it this way if you want, but I think usb_get_dma_device would > be easier to use if its argument was a pointer to struct usb_interface > or (even better) a pointer to a usb_interface's embedded struct device. > Then you wouldn't need to compute udev, and the same would be true for > other callers. It seemed natural to me to use usb_device, because it contains the bus pointer. But maybe a little wrapper for usb_interface in the header file makes things easier to read. I'll wait a bit for other reviews to come in. Best regards Thomas > > Alan Stern > _______________________________________________ > dri-devel mailing list > dri-devel@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/dri-devel >
On Thu, 25 Feb 2021 08:57:14 +0100, Thomas Zimmermann wrote: > > Hi > > Am 24.02.21 um 16:21 schrieb Alan Stern: > > On Wed, Feb 24, 2021 at 10:23:04AM +0100, Thomas Zimmermann wrote: > >> USB devices cannot perform DMA and hence have no dma_mask set in their > >> device structure. Therefore importing dmabuf into a USB-based driver > >> fails, which breaks joining and mirroring of display in X11. > >> > >> For USB devices, pick the associated USB controller as attachment device. > >> This allows the DRM import helpers to perform the DMA setup. If the DMA > >> controller does not support DMA transfers, we're out of luck and cannot > >> import. Our current USB-based DRM drivers don't use DMA, so the actual > >> DMA device is not important. > >> > >> Drivers should use DRM_GEM_SHMEM_DROVER_OPS_USB to initialize their > >> instance of struct drm_driver. > >> > >> Tested by joining/mirroring displays of udl and radeon un der Gnome/X11. > >> > >> v4: > >> * implement workaround with USB helper functions (Greg) > >> * use struct usb_device->bus->sysdev as DMA device (Takashi) > >> v3: > >> * drop gem_create_object > >> * use DMA mask of USB controller, if any (Daniel, Christian, Noralf) > >> v2: > >> * move fix to importer side (Christian, Daniel) > >> * update SHMEM and CMA helpers for new PRIME callbacks > >> > >> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de> > >> Fixes: 6eb0233ec2d0 ("usb: don't inherity DMA properties for USB devices") > >> Cc: Christoph Hellwig <hch@lst.de> > >> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > >> Cc: <stable@vger.kernel.org> # v5.10+ > >> --- > > > >> +struct drm_gem_object *drm_gem_prime_import_usb(struct drm_device *dev, > >> + struct dma_buf *dma_buf) > >> +{ > >> + struct usb_device *udev; > >> + struct device *dmadev; > >> + struct drm_gem_object *obj; > >> + > >> + if (!dev_is_usb(dev->dev)) > >> + return ERR_PTR(-ENODEV); > >> + udev = interface_to_usbdev(to_usb_interface(dev->dev)); > >> + > >> + dmadev = usb_get_dma_device(udev); > > > > You can do it this way if you want, but I think usb_get_dma_device would > > be easier to use if its argument was a pointer to struct usb_interface > > or (even better) a pointer to a usb_interface's embedded struct device. > > Then you wouldn't need to compute udev, and the same would be true for > > other callers. > > It seemed natural to me to use usb_device, because it contains the bus > pointer. But maybe a little wrapper for usb_interface in the header > file makes things easier to read. I'll wait a bit for other reviews to > come in. I agree with Thomas, as most of users referring to the sysdev do access in a pattern like udev->bus->sysdev, AFAIK. thanks, Takashi
Am 24.02.21 um 10:23 schrieb Thomas Zimmermann: > USB devices cannot perform DMA and hence have no dma_mask set in their > device structure. Therefore importing dmabuf into a USB-based driver > fails, which breaks joining and mirroring of display in X11. > > For USB devices, pick the associated USB controller as attachment device. > This allows the DRM import helpers to perform the DMA setup. If the DMA > controller does not support DMA transfers, we're out of luck and cannot > import. Our current USB-based DRM drivers don't use DMA, so the actual > DMA device is not important. > > Drivers should use DRM_GEM_SHMEM_DROVER_OPS_USB to initialize their > instance of struct drm_driver. > > Tested by joining/mirroring displays of udl and radeon un der Gnome/X11. > > v4: > * implement workaround with USB helper functions (Greg) > * use struct usb_device->bus->sysdev as DMA device (Takashi) > v3: > * drop gem_create_object > * use DMA mask of USB controller, if any (Daniel, Christian, Noralf) > v2: > * move fix to importer side (Christian, Daniel) > * update SHMEM and CMA helpers for new PRIME callbacks > > Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de> > Fixes: 6eb0233ec2d0 ("usb: don't inherity DMA properties for USB devices") > Cc: Christoph Hellwig <hch@lst.de> > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > Cc: <stable@vger.kernel.org> # v5.10+ I can't say much about the USB functions to use, but from the DMA-buf side this looks like the right thing to do. Feel free to stick and Acked-by: Christian König <christian.koenig@amd.com> on it. Thanks for taking care of this, Christian. > --- > drivers/gpu/drm/drm_prime.c | 38 ++++++++++++++++++++++++++++++ > drivers/gpu/drm/tiny/gm12u320.c | 2 +- > drivers/gpu/drm/udl/udl_drv.c | 2 +- > drivers/usb/core/usb.c | 29 +++++++++++++++++++++++ > include/drm/drm_gem_shmem_helper.h | 13 ++++++++++ > include/drm/drm_prime.h | 5 ++++ > include/linux/usb.h | 3 +++ > 7 files changed, 90 insertions(+), 2 deletions(-) > > diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c > index 2a54f86856af..15c82088ab4c 100644 > --- a/drivers/gpu/drm/drm_prime.c > +++ b/drivers/gpu/drm/drm_prime.c > @@ -29,6 +29,7 @@ > #include <linux/export.h> > #include <linux/dma-buf.h> > #include <linux/rbtree.h> > +#include <linux/usb.h> > > #include <drm/drm.h> > #include <drm/drm_drv.h> > @@ -1055,3 +1056,40 @@ void drm_prime_gem_destroy(struct drm_gem_object *obj, struct sg_table *sg) > dma_buf_put(dma_buf); > } > EXPORT_SYMBOL(drm_prime_gem_destroy); > + > +/** > + * drm_gem_prime_import_usb - helper library implementation of the import callback for USB devices > + * @dev: drm_device to import into > + * @dma_buf: dma-buf object to import > + * > + * This is an implementation of drm_gem_prime_import() for USB-based devices. > + * USB devices cannot perform DMA directly. This function selects the USB host > + * controller as DMA device instead. Drivers can use this as their > + * &drm_driver.gem_prime_import implementation. > + * > + * See also drm_gem_prime_import(). > + */ > +#ifdef CONFIG_USB > +struct drm_gem_object *drm_gem_prime_import_usb(struct drm_device *dev, > + struct dma_buf *dma_buf) > +{ > + struct usb_device *udev; > + struct device *dmadev; > + struct drm_gem_object *obj; > + > + if (!dev_is_usb(dev->dev)) > + return ERR_PTR(-ENODEV); > + udev = interface_to_usbdev(to_usb_interface(dev->dev)); > + > + dmadev = usb_get_dma_device(udev); > + if (drm_WARN_ONCE(dev, !dmadev, "buffer sharing not supported")) > + return ERR_PTR(-ENODEV); > + > + obj = drm_gem_prime_import_dev(dev, dma_buf, dmadev); > + > + put_device(dmadev); > + > + return obj; > +} > +EXPORT_SYMBOL(drm_gem_prime_import_usb); > +#endif > diff --git a/drivers/gpu/drm/tiny/gm12u320.c b/drivers/gpu/drm/tiny/gm12u320.c > index 0b4f4f2af1ef..99e7bd36a220 100644 > --- a/drivers/gpu/drm/tiny/gm12u320.c > +++ b/drivers/gpu/drm/tiny/gm12u320.c > @@ -611,7 +611,7 @@ static const struct drm_driver gm12u320_drm_driver = { > .minor = DRIVER_MINOR, > > .fops = &gm12u320_fops, > - DRM_GEM_SHMEM_DRIVER_OPS, > + DRM_GEM_SHMEM_DRIVER_OPS_USB, > }; > > static const struct drm_mode_config_funcs gm12u320_mode_config_funcs = { > diff --git a/drivers/gpu/drm/udl/udl_drv.c b/drivers/gpu/drm/udl/udl_drv.c > index 9269092697d8..2db483b2b199 100644 > --- a/drivers/gpu/drm/udl/udl_drv.c > +++ b/drivers/gpu/drm/udl/udl_drv.c > @@ -39,7 +39,7 @@ static const struct drm_driver driver = { > > /* GEM hooks */ > .fops = &udl_driver_fops, > - DRM_GEM_SHMEM_DRIVER_OPS, > + DRM_GEM_SHMEM_DRIVER_OPS_USB, > > .name = DRIVER_NAME, > .desc = DRIVER_DESC, > diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c > index 8f07b0516100..253bf71780fd 100644 > --- a/drivers/usb/core/usb.c > +++ b/drivers/usb/core/usb.c > @@ -748,6 +748,35 @@ void usb_put_intf(struct usb_interface *intf) > } > EXPORT_SYMBOL_GPL(usb_put_intf); > > +/** > + * usb_get_dma_device - acquire a reference on the usb device's DMA endpoint > + * @udev: usb device > + * > + * While a USB device cannot perform DMA operations by itself, many USB > + * controllers can. A call to usb_get_dma_device() returns the DMA endpoint > + * for the given USB device, if any. The returned device structure should be > + * released with put_device(). > + * > + * Returns: A reference to the usb device's DMA endpoint; or NULL if none > + * exists. > + */ > +struct device *usb_get_dma_device(struct usb_device *udev) > +{ > + struct device *dmadev; > + > + if (!udev->bus) > + return NULL; > + > + dmadev = get_device(udev->bus->sysdev); > + if (!dmadev || !dmadev->dma_mask) { > + put_device(dmadev); > + return NULL; > + } > + > + return dmadev; > +} > +EXPORT_SYMBOL_GPL(usb_get_dma_device); > + > /* USB device locking > * > * USB devices and interfaces are locked using the semaphore in their > diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h > index 434328d8a0d9..09d12f632cad 100644 > --- a/include/drm/drm_gem_shmem_helper.h > +++ b/include/drm/drm_gem_shmem_helper.h > @@ -162,4 +162,17 @@ struct sg_table *drm_gem_shmem_get_pages_sgt(struct drm_gem_object *obj); > .gem_prime_mmap = drm_gem_prime_mmap, \ > .dumb_create = drm_gem_shmem_dumb_create > > +#ifdef CONFIG_USB > +/** > + * DRM_GEM_SHMEM_DRIVER_OPS_USB - Default shmem GEM operations for USB devices > + * > + * This macro provides a shortcut for setting the shmem GEM operations in > + * the &drm_driver structure. Drivers for USB-based devices should use this > + * macro instead of &DRM_GEM_SHMEM_DRIVER_OPS. > + */ > +#define DRM_GEM_SHMEM_DRIVER_OPS_USB \ > + DRM_GEM_SHMEM_DRIVER_OPS, \ > + .gem_prime_import = drm_gem_prime_import_usb > +#endif > + > #endif /* __DRM_GEM_SHMEM_HELPER_H__ */ > diff --git a/include/drm/drm_prime.h b/include/drm/drm_prime.h > index 54f2c58305d2..b42e07edd9e6 100644 > --- a/include/drm/drm_prime.h > +++ b/include/drm/drm_prime.h > @@ -110,4 +110,9 @@ int drm_prime_sg_to_page_array(struct sg_table *sgt, struct page **pages, > int drm_prime_sg_to_dma_addr_array(struct sg_table *sgt, dma_addr_t *addrs, > int max_pages); > > +#ifdef CONFIG_USB > +struct drm_gem_object *drm_gem_prime_import_usb(struct drm_device *dev, > + struct dma_buf *dma_buf); > +#endif > + > #endif /* __DRM_PRIME_H__ */ > diff --git a/include/linux/usb.h b/include/linux/usb.h > index 7d72c4e0713c..a9bd698c8839 100644 > --- a/include/linux/usb.h > +++ b/include/linux/usb.h > @@ -711,6 +711,7 @@ struct usb_device { > unsigned use_generic_driver:1; > }; > #define to_usb_device(d) container_of(d, struct usb_device, dev) > +#define dev_is_usb(d) ((d)->bus == &usb_bus_type) > > static inline struct usb_device *interface_to_usbdev(struct usb_interface *intf) > { > @@ -746,6 +747,8 @@ extern int usb_lock_device_for_reset(struct usb_device *udev, > extern int usb_reset_device(struct usb_device *dev); > extern void usb_queue_reset_device(struct usb_interface *dev); > > +extern struct device *usb_get_dma_device(struct usb_device *udev); > + > #ifdef CONFIG_ACPI > extern int usb_acpi_set_power_state(struct usb_device *hdev, int index, > bool enable);
On Wed, Feb 24, 2021 at 10:23 AM Thomas Zimmermann <tzimmermann@suse.de> wrote: > > USB devices cannot perform DMA and hence have no dma_mask set in their > device structure. Therefore importing dmabuf into a USB-based driver > fails, which breaks joining and mirroring of display in X11. > > For USB devices, pick the associated USB controller as attachment device. > This allows the DRM import helpers to perform the DMA setup. If the DMA > controller does not support DMA transfers, we're out of luck and cannot > import. Our current USB-based DRM drivers don't use DMA, so the actual > DMA device is not important. > > Drivers should use DRM_GEM_SHMEM_DROVER_OPS_USB to initialize their > instance of struct drm_driver. > > Tested by joining/mirroring displays of udl and radeon un der Gnome/X11. > > v4: > * implement workaround with USB helper functions (Greg) > * use struct usb_device->bus->sysdev as DMA device (Takashi) > v3: > * drop gem_create_object > * use DMA mask of USB controller, if any (Daniel, Christian, Noralf) > v2: > * move fix to importer side (Christian, Daniel) > * update SHMEM and CMA helpers for new PRIME callbacks > > Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de> > Fixes: 6eb0233ec2d0 ("usb: don't inherity DMA properties for USB devices") > Cc: Christoph Hellwig <hch@lst.de> > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > Cc: <stable@vger.kernel.org> # v5.10+ > --- > drivers/gpu/drm/drm_prime.c | 38 ++++++++++++++++++++++++++++++ > drivers/gpu/drm/tiny/gm12u320.c | 2 +- > drivers/gpu/drm/udl/udl_drv.c | 2 +- > drivers/usb/core/usb.c | 29 +++++++++++++++++++++++ > include/drm/drm_gem_shmem_helper.h | 13 ++++++++++ > include/drm/drm_prime.h | 5 ++++ > include/linux/usb.h | 3 +++ > 7 files changed, 90 insertions(+), 2 deletions(-) > > diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c > index 2a54f86856af..15c82088ab4c 100644 > --- a/drivers/gpu/drm/drm_prime.c > +++ b/drivers/gpu/drm/drm_prime.c > @@ -29,6 +29,7 @@ > #include <linux/export.h> > #include <linux/dma-buf.h> > #include <linux/rbtree.h> > +#include <linux/usb.h> > > #include <drm/drm.h> > #include <drm/drm_drv.h> > @@ -1055,3 +1056,40 @@ void drm_prime_gem_destroy(struct drm_gem_object *obj, struct sg_table *sg) > dma_buf_put(dma_buf); > } > EXPORT_SYMBOL(drm_prime_gem_destroy); > + > +/** > + * drm_gem_prime_import_usb - helper library implementation of the import callback for USB devices > + * @dev: drm_device to import into > + * @dma_buf: dma-buf object to import > + * > + * This is an implementation of drm_gem_prime_import() for USB-based devices. > + * USB devices cannot perform DMA directly. This function selects the USB host > + * controller as DMA device instead. Drivers can use this as their > + * &drm_driver.gem_prime_import implementation. We're still just papering over drm_prime.c here, and this kerneldoc here is sounding way too much like this is a sensible thing to do and doesn't mention the fundamental problem. I'd do something like the below as the entire kerneldoc: <doc> FIXME: drm_gem_prime_fd_to_handle() and drm_gem_prime_handle_to_fd() require that importers call dma_buf_attach() even if they never do actual device DMA, but only CPU access through dma_buf_vmap(). Fixing this is a bit more involved, since the import/export cache is also tied to &drm_gem_object.import_attach. Meanwhile this function here can be used to paper over this problem for USB devices by fishing out the USB host controller device, as long as that supports DMA. Otherwise importing can still needlessly fail. </doc> Since we do not actually have usb drm drivers that do dma I don't want to give people wrong impressions about what's going on here. I still think the better approach would be to copypaste this hack into each of the tree drivers, with the above as a comment, since sharing bad code isn't a good idea imo - all that does is hide the problem and make the next person feel like it's all peachy. But also ok if there's a giantic warning label on the shared code. With that: Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch> > + * > + * See also drm_gem_prime_import(). > + */ > +#ifdef CONFIG_USB > +struct drm_gem_object *drm_gem_prime_import_usb(struct drm_device *dev, > + struct dma_buf *dma_buf) > +{ > + struct usb_device *udev; > + struct device *dmadev; > + struct drm_gem_object *obj; > + > + if (!dev_is_usb(dev->dev)) > + return ERR_PTR(-ENODEV); > + udev = interface_to_usbdev(to_usb_interface(dev->dev)); > + > + dmadev = usb_get_dma_device(udev); > + if (drm_WARN_ONCE(dev, !dmadev, "buffer sharing not supported")) > + return ERR_PTR(-ENODEV); > + > + obj = drm_gem_prime_import_dev(dev, dma_buf, dmadev); > + > + put_device(dmadev); > + > + return obj; > +} > +EXPORT_SYMBOL(drm_gem_prime_import_usb); > +#endif > diff --git a/drivers/gpu/drm/tiny/gm12u320.c b/drivers/gpu/drm/tiny/gm12u320.c > index 0b4f4f2af1ef..99e7bd36a220 100644 > --- a/drivers/gpu/drm/tiny/gm12u320.c > +++ b/drivers/gpu/drm/tiny/gm12u320.c > @@ -611,7 +611,7 @@ static const struct drm_driver gm12u320_drm_driver = { > .minor = DRIVER_MINOR, > > .fops = &gm12u320_fops, > - DRM_GEM_SHMEM_DRIVER_OPS, > + DRM_GEM_SHMEM_DRIVER_OPS_USB, > }; > > static const struct drm_mode_config_funcs gm12u320_mode_config_funcs = { > diff --git a/drivers/gpu/drm/udl/udl_drv.c b/drivers/gpu/drm/udl/udl_drv.c > index 9269092697d8..2db483b2b199 100644 > --- a/drivers/gpu/drm/udl/udl_drv.c > +++ b/drivers/gpu/drm/udl/udl_drv.c > @@ -39,7 +39,7 @@ static const struct drm_driver driver = { > > /* GEM hooks */ > .fops = &udl_driver_fops, > - DRM_GEM_SHMEM_DRIVER_OPS, > + DRM_GEM_SHMEM_DRIVER_OPS_USB, > > .name = DRIVER_NAME, > .desc = DRIVER_DESC, > diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c > index 8f07b0516100..253bf71780fd 100644 > --- a/drivers/usb/core/usb.c > +++ b/drivers/usb/core/usb.c > @@ -748,6 +748,35 @@ void usb_put_intf(struct usb_interface *intf) > } > EXPORT_SYMBOL_GPL(usb_put_intf); > > +/** > + * usb_get_dma_device - acquire a reference on the usb device's DMA endpoint > + * @udev: usb device > + * > + * While a USB device cannot perform DMA operations by itself, many USB > + * controllers can. A call to usb_get_dma_device() returns the DMA endpoint > + * for the given USB device, if any. The returned device structure should be > + * released with put_device(). > + * > + * Returns: A reference to the usb device's DMA endpoint; or NULL if none > + * exists. > + */ > +struct device *usb_get_dma_device(struct usb_device *udev) > +{ > + struct device *dmadev; > + > + if (!udev->bus) > + return NULL; > + > + dmadev = get_device(udev->bus->sysdev); > + if (!dmadev || !dmadev->dma_mask) { > + put_device(dmadev); > + return NULL; > + } > + > + return dmadev; > +} > +EXPORT_SYMBOL_GPL(usb_get_dma_device); > + > /* USB device locking > * > * USB devices and interfaces are locked using the semaphore in their > diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h > index 434328d8a0d9..09d12f632cad 100644 > --- a/include/drm/drm_gem_shmem_helper.h > +++ b/include/drm/drm_gem_shmem_helper.h > @@ -162,4 +162,17 @@ struct sg_table *drm_gem_shmem_get_pages_sgt(struct drm_gem_object *obj); > .gem_prime_mmap = drm_gem_prime_mmap, \ > .dumb_create = drm_gem_shmem_dumb_create > > +#ifdef CONFIG_USB > +/** > + * DRM_GEM_SHMEM_DRIVER_OPS_USB - Default shmem GEM operations for USB devices > + * > + * This macro provides a shortcut for setting the shmem GEM operations in > + * the &drm_driver structure. Drivers for USB-based devices should use this > + * macro instead of &DRM_GEM_SHMEM_DRIVER_OPS. > + */ > +#define DRM_GEM_SHMEM_DRIVER_OPS_USB \ > + DRM_GEM_SHMEM_DRIVER_OPS, \ > + .gem_prime_import = drm_gem_prime_import_usb > +#endif > + > #endif /* __DRM_GEM_SHMEM_HELPER_H__ */ > diff --git a/include/drm/drm_prime.h b/include/drm/drm_prime.h > index 54f2c58305d2..b42e07edd9e6 100644 > --- a/include/drm/drm_prime.h > +++ b/include/drm/drm_prime.h > @@ -110,4 +110,9 @@ int drm_prime_sg_to_page_array(struct sg_table *sgt, struct page **pages, > int drm_prime_sg_to_dma_addr_array(struct sg_table *sgt, dma_addr_t *addrs, > int max_pages); > > +#ifdef CONFIG_USB > +struct drm_gem_object *drm_gem_prime_import_usb(struct drm_device *dev, > + struct dma_buf *dma_buf); > +#endif > + > #endif /* __DRM_PRIME_H__ */ > diff --git a/include/linux/usb.h b/include/linux/usb.h > index 7d72c4e0713c..a9bd698c8839 100644 > --- a/include/linux/usb.h > +++ b/include/linux/usb.h > @@ -711,6 +711,7 @@ struct usb_device { > unsigned use_generic_driver:1; > }; > #define to_usb_device(d) container_of(d, struct usb_device, dev) > +#define dev_is_usb(d) ((d)->bus == &usb_bus_type) > > static inline struct usb_device *interface_to_usbdev(struct usb_interface *intf) > { > @@ -746,6 +747,8 @@ extern int usb_lock_device_for_reset(struct usb_device *udev, > extern int usb_reset_device(struct usb_device *dev); > extern void usb_queue_reset_device(struct usb_interface *dev); > > +extern struct device *usb_get_dma_device(struct usb_device *udev); > + > #ifdef CONFIG_ACPI > extern int usb_acpi_set_power_state(struct usb_device *hdev, int index, > bool enable); > -- > 2.30.1 >
Hi! > USB devices cannot perform DMA and hence have no dma_mask set in their > device structure. Therefore importing dmabuf into a USB-based driver > fails, which breaks joining and mirroring of display in X11. > > For USB devices, pick the associated USB controller as attachment device. > This allows the DRM import helpers to perform the DMA setup. If the DMA > controller does not support DMA transfers, we're out of luck and cannot > import. Our current USB-based DRM drivers don't use DMA, so the actual > DMA device is not important. > > Drivers should use DRM_GEM_SHMEM_DROVER_OPS_USB to initialize their > instance of struct drm_driver. > > Tested by joining/mirroring displays of udl and radeon un der > Gnome/X11. Thanks for doing this. Tested-by: Pavel Machek <pavel@ucw.cz> Best regards, Pavel
On Thu, Feb 25, 2021 at 09:23:05AM +0100, Takashi Iwai wrote: > On Thu, 25 Feb 2021 08:57:14 +0100, > Thomas Zimmermann wrote: > > > > Hi > > > > Am 24.02.21 um 16:21 schrieb Alan Stern: > > > On Wed, Feb 24, 2021 at 10:23:04AM +0100, Thomas Zimmermann wrote: > > >> USB devices cannot perform DMA and hence have no dma_mask set in their > > >> device structure. Therefore importing dmabuf into a USB-based driver > > >> fails, which breaks joining and mirroring of display in X11. > > >> > > >> For USB devices, pick the associated USB controller as attachment device. > > >> This allows the DRM import helpers to perform the DMA setup. If the DMA > > >> controller does not support DMA transfers, we're out of luck and cannot > > >> import. Our current USB-based DRM drivers don't use DMA, so the actual > > >> DMA device is not important. > > >> > > >> Drivers should use DRM_GEM_SHMEM_DROVER_OPS_USB to initialize their > > >> instance of struct drm_driver. > > >> > > >> Tested by joining/mirroring displays of udl and radeon un der Gnome/X11. > > >> > > >> v4: > > >> * implement workaround with USB helper functions (Greg) > > >> * use struct usb_device->bus->sysdev as DMA device (Takashi) > > >> v3: > > >> * drop gem_create_object > > >> * use DMA mask of USB controller, if any (Daniel, Christian, Noralf) > > >> v2: > > >> * move fix to importer side (Christian, Daniel) > > >> * update SHMEM and CMA helpers for new PRIME callbacks > > >> > > >> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de> > > >> Fixes: 6eb0233ec2d0 ("usb: don't inherity DMA properties for USB devices") > > >> Cc: Christoph Hellwig <hch@lst.de> > > >> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > > >> Cc: <stable@vger.kernel.org> # v5.10+ > > >> --- > > > > > >> +struct drm_gem_object *drm_gem_prime_import_usb(struct drm_device *dev, > > >> + struct dma_buf *dma_buf) > > >> +{ > > >> + struct usb_device *udev; > > >> + struct device *dmadev; > > >> + struct drm_gem_object *obj; > > >> + > > >> + if (!dev_is_usb(dev->dev)) > > >> + return ERR_PTR(-ENODEV); > > >> + udev = interface_to_usbdev(to_usb_interface(dev->dev)); > > >> + > > >> + dmadev = usb_get_dma_device(udev); > > > > > > You can do it this way if you want, but I think usb_get_dma_device would > > > be easier to use if its argument was a pointer to struct usb_interface > > > or (even better) a pointer to a usb_interface's embedded struct device. > > > Then you wouldn't need to compute udev, and the same would be true for > > > other callers. > > > > It seemed natural to me to use usb_device, because it contains the bus > > pointer. But maybe a little wrapper for usb_interface in the header > > file makes things easier to read. I'll wait a bit for other reviews to > > come in. > > I agree with Thomas, as most of users referring to the sysdev do > access in a pattern like udev->bus->sysdev, AFAIK. Apart from the USB core and host/gadget controller drivers, there appears to be only one reference to sysdev for a USB device: the one in usb-storage (and that one really should be dmadev). In general, I expect callers of the new routine would be drivers that bind to a USB interface (like usb-storage), not to a USB device. So they would naturally have the interface pointer handy. But the routine could be written in a different way. If it took a pointer to struct device as its argument, it could easily tell whether that structure was embedded in a usb_device or a usb_interface struct, and do the right thing either way. Or there could be two routines: one taking a usb_device pointer and one taking a usb_interface pointer. The idea here is to make the routine as easy as possible for callers. If this means making the routine a little longer, that's okay -- there's only one copy of the routine but there could be lots of callers. Alan Stern
Greg, do you have comments on this patch? Am 24.02.21 um 10:23 schrieb Thomas Zimmermann: > USB devices cannot perform DMA and hence have no dma_mask set in their > device structure. Therefore importing dmabuf into a USB-based driver > fails, which breaks joining and mirroring of display in X11. > > For USB devices, pick the associated USB controller as attachment device. > This allows the DRM import helpers to perform the DMA setup. If the DMA > controller does not support DMA transfers, we're out of luck and cannot > import. Our current USB-based DRM drivers don't use DMA, so the actual > DMA device is not important. > > Drivers should use DRM_GEM_SHMEM_DROVER_OPS_USB to initialize their > instance of struct drm_driver. > > Tested by joining/mirroring displays of udl and radeon un der Gnome/X11. > > v4: > * implement workaround with USB helper functions (Greg) > * use struct usb_device->bus->sysdev as DMA device (Takashi) > v3: > * drop gem_create_object > * use DMA mask of USB controller, if any (Daniel, Christian, Noralf) > v2: > * move fix to importer side (Christian, Daniel) > * update SHMEM and CMA helpers for new PRIME callbacks > > Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de> > Fixes: 6eb0233ec2d0 ("usb: don't inherity DMA properties for USB devices") > Cc: Christoph Hellwig <hch@lst.de> > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > Cc: <stable@vger.kernel.org> # v5.10+ > --- > drivers/gpu/drm/drm_prime.c | 38 ++++++++++++++++++++++++++++++ > drivers/gpu/drm/tiny/gm12u320.c | 2 +- > drivers/gpu/drm/udl/udl_drv.c | 2 +- > drivers/usb/core/usb.c | 29 +++++++++++++++++++++++ > include/drm/drm_gem_shmem_helper.h | 13 ++++++++++ > include/drm/drm_prime.h | 5 ++++ > include/linux/usb.h | 3 +++ > 7 files changed, 90 insertions(+), 2 deletions(-) > > diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c > index 2a54f86856af..15c82088ab4c 100644 > --- a/drivers/gpu/drm/drm_prime.c > +++ b/drivers/gpu/drm/drm_prime.c > @@ -29,6 +29,7 @@ > #include <linux/export.h> > #include <linux/dma-buf.h> > #include <linux/rbtree.h> > +#include <linux/usb.h> > > #include <drm/drm.h> > #include <drm/drm_drv.h> > @@ -1055,3 +1056,40 @@ void drm_prime_gem_destroy(struct drm_gem_object *obj, struct sg_table *sg) > dma_buf_put(dma_buf); > } > EXPORT_SYMBOL(drm_prime_gem_destroy); > + > +/** > + * drm_gem_prime_import_usb - helper library implementation of the import callback for USB devices > + * @dev: drm_device to import into > + * @dma_buf: dma-buf object to import > + * > + * This is an implementation of drm_gem_prime_import() for USB-based devices. > + * USB devices cannot perform DMA directly. This function selects the USB host > + * controller as DMA device instead. Drivers can use this as their > + * &drm_driver.gem_prime_import implementation. > + * > + * See also drm_gem_prime_import(). > + */ > +#ifdef CONFIG_USB > +struct drm_gem_object *drm_gem_prime_import_usb(struct drm_device *dev, > + struct dma_buf *dma_buf) > +{ > + struct usb_device *udev; > + struct device *dmadev; > + struct drm_gem_object *obj; > + > + if (!dev_is_usb(dev->dev)) > + return ERR_PTR(-ENODEV); > + udev = interface_to_usbdev(to_usb_interface(dev->dev)); > + > + dmadev = usb_get_dma_device(udev); > + if (drm_WARN_ONCE(dev, !dmadev, "buffer sharing not supported")) > + return ERR_PTR(-ENODEV); > + > + obj = drm_gem_prime_import_dev(dev, dma_buf, dmadev); > + > + put_device(dmadev); > + > + return obj; > +} > +EXPORT_SYMBOL(drm_gem_prime_import_usb); > +#endif > diff --git a/drivers/gpu/drm/tiny/gm12u320.c b/drivers/gpu/drm/tiny/gm12u320.c > index 0b4f4f2af1ef..99e7bd36a220 100644 > --- a/drivers/gpu/drm/tiny/gm12u320.c > +++ b/drivers/gpu/drm/tiny/gm12u320.c > @@ -611,7 +611,7 @@ static const struct drm_driver gm12u320_drm_driver = { > .minor = DRIVER_MINOR, > > .fops = &gm12u320_fops, > - DRM_GEM_SHMEM_DRIVER_OPS, > + DRM_GEM_SHMEM_DRIVER_OPS_USB, > }; > > static const struct drm_mode_config_funcs gm12u320_mode_config_funcs = { > diff --git a/drivers/gpu/drm/udl/udl_drv.c b/drivers/gpu/drm/udl/udl_drv.c > index 9269092697d8..2db483b2b199 100644 > --- a/drivers/gpu/drm/udl/udl_drv.c > +++ b/drivers/gpu/drm/udl/udl_drv.c > @@ -39,7 +39,7 @@ static const struct drm_driver driver = { > > /* GEM hooks */ > .fops = &udl_driver_fops, > - DRM_GEM_SHMEM_DRIVER_OPS, > + DRM_GEM_SHMEM_DRIVER_OPS_USB, > > .name = DRIVER_NAME, > .desc = DRIVER_DESC, > diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c > index 8f07b0516100..253bf71780fd 100644 > --- a/drivers/usb/core/usb.c > +++ b/drivers/usb/core/usb.c > @@ -748,6 +748,35 @@ void usb_put_intf(struct usb_interface *intf) > } > EXPORT_SYMBOL_GPL(usb_put_intf); > > +/** > + * usb_get_dma_device - acquire a reference on the usb device's DMA endpoint > + * @udev: usb device > + * > + * While a USB device cannot perform DMA operations by itself, many USB > + * controllers can. A call to usb_get_dma_device() returns the DMA endpoint > + * for the given USB device, if any. The returned device structure should be > + * released with put_device(). > + * > + * Returns: A reference to the usb device's DMA endpoint; or NULL if none > + * exists. > + */ > +struct device *usb_get_dma_device(struct usb_device *udev) > +{ > + struct device *dmadev; > + > + if (!udev->bus) > + return NULL; > + > + dmadev = get_device(udev->bus->sysdev); > + if (!dmadev || !dmadev->dma_mask) { > + put_device(dmadev); > + return NULL; > + } > + > + return dmadev; > +} > +EXPORT_SYMBOL_GPL(usb_get_dma_device); > + > /* USB device locking > * > * USB devices and interfaces are locked using the semaphore in their > diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h > index 434328d8a0d9..09d12f632cad 100644 > --- a/include/drm/drm_gem_shmem_helper.h > +++ b/include/drm/drm_gem_shmem_helper.h > @@ -162,4 +162,17 @@ struct sg_table *drm_gem_shmem_get_pages_sgt(struct drm_gem_object *obj); > .gem_prime_mmap = drm_gem_prime_mmap, \ > .dumb_create = drm_gem_shmem_dumb_create > > +#ifdef CONFIG_USB > +/** > + * DRM_GEM_SHMEM_DRIVER_OPS_USB - Default shmem GEM operations for USB devices > + * > + * This macro provides a shortcut for setting the shmem GEM operations in > + * the &drm_driver structure. Drivers for USB-based devices should use this > + * macro instead of &DRM_GEM_SHMEM_DRIVER_OPS. > + */ > +#define DRM_GEM_SHMEM_DRIVER_OPS_USB \ > + DRM_GEM_SHMEM_DRIVER_OPS, \ > + .gem_prime_import = drm_gem_prime_import_usb > +#endif > + > #endif /* __DRM_GEM_SHMEM_HELPER_H__ */ > diff --git a/include/drm/drm_prime.h b/include/drm/drm_prime.h > index 54f2c58305d2..b42e07edd9e6 100644 > --- a/include/drm/drm_prime.h > +++ b/include/drm/drm_prime.h > @@ -110,4 +110,9 @@ int drm_prime_sg_to_page_array(struct sg_table *sgt, struct page **pages, > int drm_prime_sg_to_dma_addr_array(struct sg_table *sgt, dma_addr_t *addrs, > int max_pages); > > +#ifdef CONFIG_USB > +struct drm_gem_object *drm_gem_prime_import_usb(struct drm_device *dev, > + struct dma_buf *dma_buf); > +#endif > + > #endif /* __DRM_PRIME_H__ */ > diff --git a/include/linux/usb.h b/include/linux/usb.h > index 7d72c4e0713c..a9bd698c8839 100644 > --- a/include/linux/usb.h > +++ b/include/linux/usb.h > @@ -711,6 +711,7 @@ struct usb_device { > unsigned use_generic_driver:1; > }; > #define to_usb_device(d) container_of(d, struct usb_device, dev) > +#define dev_is_usb(d) ((d)->bus == &usb_bus_type) > > static inline struct usb_device *interface_to_usbdev(struct usb_interface *intf) > { > @@ -746,6 +747,8 @@ extern int usb_lock_device_for_reset(struct usb_device *udev, > extern int usb_reset_device(struct usb_device *dev); > extern void usb_queue_reset_device(struct usb_interface *dev); > > +extern struct device *usb_get_dma_device(struct usb_device *udev); > + > #ifdef CONFIG_ACPI > extern int usb_acpi_set_power_state(struct usb_device *hdev, int index, > bool enable); >
On Fri, Feb 26, 2021 at 08:59:50AM +0100, Thomas Zimmermann wrote:
> Greg, do you have comments on this patch?
I'll defer to Alan's comments so far, I would like to see that
addressed.
thanks,
greg k-h
diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c index 2a54f86856af..15c82088ab4c 100644 --- a/drivers/gpu/drm/drm_prime.c +++ b/drivers/gpu/drm/drm_prime.c @@ -29,6 +29,7 @@ #include <linux/export.h> #include <linux/dma-buf.h> #include <linux/rbtree.h> +#include <linux/usb.h> #include <drm/drm.h> #include <drm/drm_drv.h> @@ -1055,3 +1056,40 @@ void drm_prime_gem_destroy(struct drm_gem_object *obj, struct sg_table *sg) dma_buf_put(dma_buf); } EXPORT_SYMBOL(drm_prime_gem_destroy); + +/** + * drm_gem_prime_import_usb - helper library implementation of the import callback for USB devices + * @dev: drm_device to import into + * @dma_buf: dma-buf object to import + * + * This is an implementation of drm_gem_prime_import() for USB-based devices. + * USB devices cannot perform DMA directly. This function selects the USB host + * controller as DMA device instead. Drivers can use this as their + * &drm_driver.gem_prime_import implementation. + * + * See also drm_gem_prime_import(). + */ +#ifdef CONFIG_USB +struct drm_gem_object *drm_gem_prime_import_usb(struct drm_device *dev, + struct dma_buf *dma_buf) +{ + struct usb_device *udev; + struct device *dmadev; + struct drm_gem_object *obj; + + if (!dev_is_usb(dev->dev)) + return ERR_PTR(-ENODEV); + udev = interface_to_usbdev(to_usb_interface(dev->dev)); + + dmadev = usb_get_dma_device(udev); + if (drm_WARN_ONCE(dev, !dmadev, "buffer sharing not supported")) + return ERR_PTR(-ENODEV); + + obj = drm_gem_prime_import_dev(dev, dma_buf, dmadev); + + put_device(dmadev); + + return obj; +} +EXPORT_SYMBOL(drm_gem_prime_import_usb); +#endif diff --git a/drivers/gpu/drm/tiny/gm12u320.c b/drivers/gpu/drm/tiny/gm12u320.c index 0b4f4f2af1ef..99e7bd36a220 100644 --- a/drivers/gpu/drm/tiny/gm12u320.c +++ b/drivers/gpu/drm/tiny/gm12u320.c @@ -611,7 +611,7 @@ static const struct drm_driver gm12u320_drm_driver = { .minor = DRIVER_MINOR, .fops = &gm12u320_fops, - DRM_GEM_SHMEM_DRIVER_OPS, + DRM_GEM_SHMEM_DRIVER_OPS_USB, }; static const struct drm_mode_config_funcs gm12u320_mode_config_funcs = { diff --git a/drivers/gpu/drm/udl/udl_drv.c b/drivers/gpu/drm/udl/udl_drv.c index 9269092697d8..2db483b2b199 100644 --- a/drivers/gpu/drm/udl/udl_drv.c +++ b/drivers/gpu/drm/udl/udl_drv.c @@ -39,7 +39,7 @@ static const struct drm_driver driver = { /* GEM hooks */ .fops = &udl_driver_fops, - DRM_GEM_SHMEM_DRIVER_OPS, + DRM_GEM_SHMEM_DRIVER_OPS_USB, .name = DRIVER_NAME, .desc = DRIVER_DESC, diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c index 8f07b0516100..253bf71780fd 100644 --- a/drivers/usb/core/usb.c +++ b/drivers/usb/core/usb.c @@ -748,6 +748,35 @@ void usb_put_intf(struct usb_interface *intf) } EXPORT_SYMBOL_GPL(usb_put_intf); +/** + * usb_get_dma_device - acquire a reference on the usb device's DMA endpoint + * @udev: usb device + * + * While a USB device cannot perform DMA operations by itself, many USB + * controllers can. A call to usb_get_dma_device() returns the DMA endpoint + * for the given USB device, if any. The returned device structure should be + * released with put_device(). + * + * Returns: A reference to the usb device's DMA endpoint; or NULL if none + * exists. + */ +struct device *usb_get_dma_device(struct usb_device *udev) +{ + struct device *dmadev; + + if (!udev->bus) + return NULL; + + dmadev = get_device(udev->bus->sysdev); + if (!dmadev || !dmadev->dma_mask) { + put_device(dmadev); + return NULL; + } + + return dmadev; +} +EXPORT_SYMBOL_GPL(usb_get_dma_device); + /* USB device locking * * USB devices and interfaces are locked using the semaphore in their diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h index 434328d8a0d9..09d12f632cad 100644 --- a/include/drm/drm_gem_shmem_helper.h +++ b/include/drm/drm_gem_shmem_helper.h @@ -162,4 +162,17 @@ struct sg_table *drm_gem_shmem_get_pages_sgt(struct drm_gem_object *obj); .gem_prime_mmap = drm_gem_prime_mmap, \ .dumb_create = drm_gem_shmem_dumb_create +#ifdef CONFIG_USB +/** + * DRM_GEM_SHMEM_DRIVER_OPS_USB - Default shmem GEM operations for USB devices + * + * This macro provides a shortcut for setting the shmem GEM operations in + * the &drm_driver structure. Drivers for USB-based devices should use this + * macro instead of &DRM_GEM_SHMEM_DRIVER_OPS. + */ +#define DRM_GEM_SHMEM_DRIVER_OPS_USB \ + DRM_GEM_SHMEM_DRIVER_OPS, \ + .gem_prime_import = drm_gem_prime_import_usb +#endif + #endif /* __DRM_GEM_SHMEM_HELPER_H__ */ diff --git a/include/drm/drm_prime.h b/include/drm/drm_prime.h index 54f2c58305d2..b42e07edd9e6 100644 --- a/include/drm/drm_prime.h +++ b/include/drm/drm_prime.h @@ -110,4 +110,9 @@ int drm_prime_sg_to_page_array(struct sg_table *sgt, struct page **pages, int drm_prime_sg_to_dma_addr_array(struct sg_table *sgt, dma_addr_t *addrs, int max_pages); +#ifdef CONFIG_USB +struct drm_gem_object *drm_gem_prime_import_usb(struct drm_device *dev, + struct dma_buf *dma_buf); +#endif + #endif /* __DRM_PRIME_H__ */ diff --git a/include/linux/usb.h b/include/linux/usb.h index 7d72c4e0713c..a9bd698c8839 100644 --- a/include/linux/usb.h +++ b/include/linux/usb.h @@ -711,6 +711,7 @@ struct usb_device { unsigned use_generic_driver:1; }; #define to_usb_device(d) container_of(d, struct usb_device, dev) +#define dev_is_usb(d) ((d)->bus == &usb_bus_type) static inline struct usb_device *interface_to_usbdev(struct usb_interface *intf) { @@ -746,6 +747,8 @@ extern int usb_lock_device_for_reset(struct usb_device *udev, extern int usb_reset_device(struct usb_device *dev); extern void usb_queue_reset_device(struct usb_interface *dev); +extern struct device *usb_get_dma_device(struct usb_device *udev); + #ifdef CONFIG_ACPI extern int usb_acpi_set_power_state(struct usb_device *hdev, int index, bool enable);
USB devices cannot perform DMA and hence have no dma_mask set in their device structure. Therefore importing dmabuf into a USB-based driver fails, which breaks joining and mirroring of display in X11. For USB devices, pick the associated USB controller as attachment device. This allows the DRM import helpers to perform the DMA setup. If the DMA controller does not support DMA transfers, we're out of luck and cannot import. Our current USB-based DRM drivers don't use DMA, so the actual DMA device is not important. Drivers should use DRM_GEM_SHMEM_DROVER_OPS_USB to initialize their instance of struct drm_driver. Tested by joining/mirroring displays of udl and radeon un der Gnome/X11. v4: * implement workaround with USB helper functions (Greg) * use struct usb_device->bus->sysdev as DMA device (Takashi) v3: * drop gem_create_object * use DMA mask of USB controller, if any (Daniel, Christian, Noralf) v2: * move fix to importer side (Christian, Daniel) * update SHMEM and CMA helpers for new PRIME callbacks Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de> Fixes: 6eb0233ec2d0 ("usb: don't inherity DMA properties for USB devices") Cc: Christoph Hellwig <hch@lst.de> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: <stable@vger.kernel.org> # v5.10+ --- drivers/gpu/drm/drm_prime.c | 38 ++++++++++++++++++++++++++++++ drivers/gpu/drm/tiny/gm12u320.c | 2 +- drivers/gpu/drm/udl/udl_drv.c | 2 +- drivers/usb/core/usb.c | 29 +++++++++++++++++++++++ include/drm/drm_gem_shmem_helper.h | 13 ++++++++++ include/drm/drm_prime.h | 5 ++++ include/linux/usb.h | 3 +++ 7 files changed, 90 insertions(+), 2 deletions(-)