[PATCH v5 1/1] drm/doc: Document DRM device reset expectations

[André Almeida]

Hi Marek,

Em 27/06/2023 15:57, Marek Olšák escreveu:
> On Tue, Jun 27, 2023, 09:23 André Almeida <andrealmeid at igalia.com 
> <mailto:andrealmeid at igalia.com>> wrote:
> 
>     +User Mode Driver
>     +----------------
>     +
>     +The UMD should check before submitting new commands to the KMD if
>     the device has
>     +been reset, and this can be checked more often if the UMD requires
>     it. After
>     +detecting a reset, UMD will then proceed to report it to the
>     application using
>     +the appropriate API error code, as explained in the section below about
>     +robustness.
> 
> 
> The UMD won't check the device status before every command submission 
> due to ioctl overhead. Instead, the KMD should skip command submission 
> and return an error that it was skipped.

I wrote like this because when reading the source code for 
vk::check_status()[0] and Gallium's si_flush_gfx_cs()[1], I was under 
the impression that UMD checks the reset status before every 
submission/flush.

Is your comment about of how things are currently implemented, or how 
they would ideally work? Either way I can apply your suggestion, I just 
want to make it clear.

[0] 
https://elixir.bootlin.com/mesa/mesa-23.1.3/source/src/vulkan/runtime/vk_device.h#L142
[1] 
https://elixir.bootlin.com/mesa/mesa-23.1.3/source/src/gallium/drivers/radeonsi/si_gfx_cs.c#L83

> 
> The only case where that won't be applicable is user queues where 
> drivers don't call into the kernel to submit work, but they do call into 
> the kernel to create a dma_fence. In that case, the call to create a 
> dma_fence can fail with an error.
> 
> Marek