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From: Pavel Machek <pavel@ucw.cz>
To: Thomas Zimmermann <tzimmermann@suse.de>
Cc: airlied@linux.ie, gregkh@linuxfoundation.org,
	dri-devel@lists.freedesktop.org, Christoph Hellwig <hch@lst.de>,
	hdegoede@redhat.com, stern@rowland.harvard.edu,
	stable@vger.kernel.org, sean@poorly.run,
	christian.koenig@amd.com
Subject: Re: [PATCH v4] drm: Use USB controller's DMA mask when importing dmabufs
Date: Thu, 25 Feb 2021 10:47:04 +0100	[thread overview]
Message-ID: <20210225094704.GA4967@amd> (raw)
In-Reply-To: <20210224092304.29932-1-tzimmermann@suse.de>


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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
-- 
http://www.livejournal.com/~pavelmachek

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WARNING: multiple messages have this Message-ID (diff)
From: Pavel Machek <pavel@ucw.cz>
To: Thomas Zimmermann <tzimmermann@suse.de>
Cc: daniel@ffwll.ch, airlied@linux.ie,
	maarten.lankhorst@linux.intel.com, mripard@kernel.org,
	sumit.semwal@linaro.org, christian.koenig@amd.com,
	gregkh@linuxfoundation.org, hdegoede@redhat.com, sean@poorly.run,
	noralf@tronnes.org, stern@rowland.harvard.edu,
	stable@vger.kernel.org, dri-devel@lists.freedesktop.org,
	Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH v4] drm: Use USB controller's DMA mask when importing dmabufs
Date: Thu, 25 Feb 2021 10:47:04 +0100	[thread overview]
Message-ID: <20210225094704.GA4967@amd> (raw)
In-Reply-To: <20210224092304.29932-1-tzimmermann@suse.de>

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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
-- 
http://www.livejournal.com/~pavelmachek

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  parent reply	other threads:[~2021-02-25  9:47 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-24  9:23 [PATCH v4] drm: Use USB controller's DMA mask when importing dmabufs Thomas Zimmermann
2021-02-24  9:23 ` Thomas Zimmermann
2021-02-24 15:21 ` Alan Stern
2021-02-24 15:21   ` Alan Stern
2021-02-25  7:57   ` Thomas Zimmermann
2021-02-25  7:57     ` Thomas Zimmermann
2021-02-25  8:23     ` Takashi Iwai
2021-02-25  8:23       ` Takashi Iwai
2021-02-25 16:18       ` Alan Stern
2021-02-25 16:18         ` Alan Stern
2021-02-25  9:19 ` Christian König
2021-02-25  9:19   ` Christian König
2021-02-25  9:36 ` Daniel Vetter
2021-02-25  9:36   ` Daniel Vetter
2021-02-25  9:47 ` Pavel Machek [this message]
2021-02-25  9:47   ` Pavel Machek
2021-02-26  7:59 ` Thomas Zimmermann
2021-02-26  7:59   ` Thomas Zimmermann
2021-02-26  8:10   ` Greg KH
2021-02-26  8:10     ` Greg KH

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