linux-kernel - Re: [PATCH 6/7] misc: bcm-vk: add Broadcom Valkyrie driver

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Date:   Tue, 27 Aug 2019 16:14:54 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Scott Branden <scott.branden@...adcom.com>
Cc:     Luis Chamberlain <mcgrof@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        David Brown <david.brown@...aro.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Shuah Khan <shuah@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Shuah Khan <skhan@...uxfoundation.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arm-msm@...r.kernel.org,
        Linux FS-devel Mailing List <linux-fsdevel@...r.kernel.org>,
        BCM Kernel Feedback <bcm-kernel-feedback-list@...adcom.com>,
        Olof Johansson <olof@...om.net>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Colin Ian King <colin.king@...onical.com>,
        Kees Cook <keescook@...omium.org>,
        Takashi Iwai <tiwai@...e.de>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>,
        Desmond Yan <desmond.yan@...adcom.com>,
        James Hu <james.hu@...adcom.com>,
        Linux Media Mailing List <linux-media@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH 6/7] misc: bcm-vk: add Broadcom Valkyrie driver

On Thu, Aug 22, 2019 at 9:25 PM Scott Branden
<scott.branden@...adcom.com> wrote:
>
> Add Broadcom Valkyrie driver offload engine.
> This driver interfaces to the Valkyrie PCIe offload engine to perform
> should offload functions as video transcoding on multiple streams
> in parallel.  Valkyrie device is booted from files loaded using
> request_firmware_into_buf mechanism.  After booted card status is updated
> and messages can then be sent to the card.
> Such messages contain scatter gather list of addresses
> to pull data from the host to perform operations on.
>
> Signed-off-by: Scott Branden <scott.branden@...adcom.com>
> Signed-off-by: Desmond Yan <desmond.yan@...adcom.com>
> Signed-off-by: James Hu <james.hu@...adcom.com>

Can you explain the decision to make this is a standalone misc driver
rather than hooking into the existing framework in drivers/media?

There is an existing interface that looks like it could fit the hardware
in include/media/v4l2-mem2mem.h. Have you considered using that?

There is also support for video transcoding using GPUs in
driver/gpu/drm/, that could also be used in theory, though it sounds
like a less optimal fit.

      Arnd