linux-kernel - Re: [PATCH V1] accel/amdxdna: Add ioctl DRM_IOCTL_AMDXDNA_GET

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Message-ID: <c048645d-480d-4b7f-8dde-efb095b2c2fa@amd.com>
Date: Tue, 26 Aug 2025 19:31:40 -0500
From: Mario Limonciello <mario.limonciello@....com>
To: Lizhi Hou <lizhi.hou@....com>, ogabbay@...nel.org,
 quic_jhugo@...cinc.com, jacek.lawrynowicz@...ux.intel.com,
 dri-devel@...ts.freedesktop.org
Cc: linux-kernel@...r.kernel.org, max.zhen@....com, sonal.santan@....com
Subject: Re: [PATCH V1] accel/amdxdna: Add ioctl DRM_IOCTL_AMDXDNA_GET_ARRAY

On 8/26/2025 1:10 PM, Lizhi Hou wrote:
> 
> On 8/26/25 10:58, Mario Limonciello wrote:
>> On 8/26/2025 12:55 PM, Lizhi Hou wrote:
>>>
>>> On 8/26/25 10:18, Mario Limonciello wrote:
>>>> On 8/25/2025 11:48 PM, Lizhi Hou wrote:
>>>>>
>>>>> On 8/25/25 14:28, Mario Limonciello wrote:
>>>>>> On 8/22/2025 12:23 PM, Lizhi Hou wrote:
>>>>>>> Add interface for applications to get information array. The 
>>>>>>> application
>>>>>>> provides a buffer pointer along with information type, maximum 
>>>>>>> number of
>>>>>>> entries and maximum size of each entry. The buffer may also 
>>>>>>> contain match
>>>>>>> conditions based on the information type. After the ioctl 
>>>>>>> completes, the
>>>>>>> actual number of entries and entry size are returned.
>>>>>>>
>>>>>>> Signed-off-by: Lizhi Hou <lizhi.hou@....com>
>>>>>>
>>>>>> How does userspace discover whether or not the new IOCTL call is 
>>>>>> supported?  Just a test call?
>>>>> The kernel header version will be used to determine whether the 
>>>>> application which uses new IOCTL will be compiled or not.
>>>>>
>>>>
>>>> But it's not actually an application compile time decision, it's a 
>>>> runtime decision.  IE I can compile an application with the headers 
>>>> on kernel 6.18 that has this, but if I try to run it on 6.15 it's 
>>>> going to barf.
>>>>
>>>> To some extent that comes with the territory, but I'm wondering if a 
>>>> better solution going forward would be for there to be a dedicated 
>>>> version command that you bump.
>>>
>>> For in-tree driver, I did not aware a common way for this other than 
>>> checking the kernel version.
>>>
>>> And here is qaic patch of adding a new IOCTL.
>>>
>>> https://github.com/torvalds/linux/ 
>>> commit/217b812364d360e1933d8485f063400e5dda7d66
>>>
>>>
>>> I know there is major, minor, patchlevel in struct drm_driver. And I 
>>> think that is not required for in-tree driver.
>>>
>>> Please let me know if I missed anything.
>>>
>>> Thanks,
>>
>> Right; so bump up one of those so that userspace can check it. Maybe 
>> "minor"?
> 
> I meant for in-tree driver, is it good enough for userspace to just 
> check kernel version?  E.g. The drm driver versions are not used by ivpu 
> or qaic.
> 

Just because they don't doesn't mean you shouldn't.

Take a look at what amdgpu does for user queues earlier this year for 
example: 100b6010d7540e

This means that a userspace application can look for that minor bump or 
newer to know the ioctl supports user queues.