Re: [PATCH v2] drm/tegra: Add kerneldoc for UAPI

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On 19.05.2018 01:24, Thierry Reding wrote:
> On Sat, May 19, 2018 at 01:18:05AM +0300, Dmitry Osipenko wrote:
>> On 19.05.2018 01:13, Thierry Reding wrote:
>>> On Fri, May 18, 2018 at 11:58:19PM +0200, Thierry Reding wrote:
>>>> On Sat, May 19, 2018 at 12:42:22AM +0300, Dmitry Osipenko wrote:
>>>>> On 18.05.2018 23:33, Thierry Reding wrote:
>>>>>> From: Thierry Reding <treding@xxxxxxxxxx>
>>>>>>
>>>>>> Document the userspace ABI with kerneldoc to provide some information on
>>>>>> how to use it.
>>>>>>
>>>>>> v2:
>>>>>> - keep GEM object creation flags for ABI compatibility
>>>>>> - fix typo in struct drm_tegra_syncpt_incr kerneldoc
>>>>>> - fix typos in struct drm_tegra_submit kerneldoc
>>>>>> - reworded some descriptions as suggested
>>>>>>
>>>>>> Signed-off-by: Thierry Reding <treding@xxxxxxxxxx>
>>>>>> ---
>>>>>>  include/uapi/drm/tegra_drm.h | 480 ++++++++++++++++++++++++++++++++++-
>>>>>>  1 file changed, 471 insertions(+), 9 deletions(-)
>>>>>>
>>>>>> diff --git a/include/uapi/drm/tegra_drm.h b/include/uapi/drm/tegra_drm.h
>>>>>> index 99e15d82d1e9..7e121c69cd9a 100644
>>>>>> --- a/include/uapi/drm/tegra_drm.h
>>>>>> +++ b/include/uapi/drm/tegra_drm.h
>>>>>> @@ -32,143 +32,605 @@ extern "C" {
>>>>>>  #define DRM_TEGRA_GEM_CREATE_TILED     (1 << 0)
>>>>>>  #define DRM_TEGRA_GEM_CREATE_BOTTOM_UP (1 << 1)
>>>>>>  
>>>>>> +/**
>>>>>> + * struct drm_tegra_gem_create - parameters for the GEM object creation IOCTL
>>>>>> + */
>>>>>>  struct drm_tegra_gem_create {
>>>>>> +	/**
>>>>>> +	 * @size:
>>>>>> +	 *
>>>>>> +	 * The size, in bytes, of the buffer object to be created.
>>>>>> +	 */
>>>>>>  	__u64 size;
>>>>>> +
>>>>>> +	/**
>>>>>> +	 * @flags:
>>>>>> +	 *
>>>>>> +	 * A bitmask of flags that influence the creation of GEM objects:
>>>>>> +	 *
>>>>>> +	 * DRM_TEGRA_GEM_CREATE_TILED
>>>>>> +	 *   Use the 16x16 tiling format for this buffer.
>>>>>> +	 *
>>>>>> +	 * DRM_TEGRA_GEM_CREATE_BOTTOM_UP
>>>>>> +	 *   The buffer has a bottom-up layout.
>>>>>> +	 */
>>>>>>  	__u32 flags;
>>>>>> +
>>>>>> +	/**
>>>>>> +	 * @handle:
>>>>>> +	 *
>>>>>> +	 * The handle of the created GEM object. Set by the kernel upon
>>>>>> +	 * successful completion of the IOCTL.
>>>>>> +	 */
>>>>>>  	__u32 handle;
>>>>>>  };
>>>>>>  
>>>>>> +/**
>>>>>> + * struct drm_tegra_gem_mmap - parameters for the GEM mmap IOCTL
>>>>>> + */
>>>>>>  struct drm_tegra_gem_mmap {
>>>>>> +	/**
>>>>>> +	 * @handle:
>>>>>> +	 *
>>>>>> +	 * Handle of the GEM object to obtain an mmap offset for.
>>>>>> +	 */
>>>>>>  	__u32 handle;
>>>>>> +
>>>>>> +	/**
>>>>>> +	 * @pad:
>>>>>> +	 *
>>>>>> +	 * Structure padding that may be used in the future. Must be 0.
>>>>>> +	 */
>>>>>>  	__u32 pad;
>>>>>> +
>>>>>> +	/**
>>>>>> +	 * @offset:
>>>>>> +	 *
>>>>>> +	 * The mmap offset for the given GEM object. Set by the kernel upon
>>>>>> +	 * successful completion of the IOCTL.
>>>>>> +	 */
>>>>>>  	__u64 offset;
>>>>>>  };
>>>>>>  
>>>>>> +/**
>>>>>> + * struct drm_tegra_syncpt_read - parameters for the read syncpoint IOCTL
>>>>>> + */
>>>>>>  struct drm_tegra_syncpt_read {
>>>>>> +	/**
>>>>>> +	 * @id:
>>>>>> +	 *
>>>>>> +	 * ID of the syncpoint to read the current value from.
>>>>>> +	 */
>>>>>>  	__u32 id;
>>>>>> +
>>>>>> +	/**
>>>>>> +	 * @value:
>>>>>> +	 *
>>>>>> +	 * The current syncpoint value. Set by the kernel upon successful
>>>>>> +	 * completion of the IOCTL.
>>>>>> +	 */
>>>>>>  	__u32 value;
>>>>>>  };
>>>>>>  
>>>>>> +/**
>>>>>> + * struct drm_tegra_syncpt_incr - parameters for the increment syncpoint IOCTL
>>>>>> + */
>>>>>>  struct drm_tegra_syncpt_incr {
>>>>>> +	/**
>>>>>> +	 * @id:
>>>>>> +	 *
>>>>>> +	 * ID of the syncpoint to increment.
>>>>>> +	 */
>>>>>>  	__u32 id;
>>>>>> +
>>>>>> +	/**
>>>>>> +	 * @pad:
>>>>>> +	 *
>>>>>> +	 * Structure padding that may be used in the future. Must be 0.
>>>>>> +	 */
>>>>>>  	__u32 pad;
>>>>>>  };
>>>>>>  
>>>>>> +/**
>>>>>> + * struct drm_tegra_syncpt_wait - parameters for the wait syncpoint IOCTL
>>>>>> + */
>>>>>>  struct drm_tegra_syncpt_wait {
>>>>>> +	/**
>>>>>> +	 * @id:
>>>>>> +	 *
>>>>>> +	 * ID of the syncpoint to wait on.
>>>>>> +	 */
>>>>>>  	__u32 id;
>>>>>> +
>>>>>> +	/**
>>>>>> +	 * @thresh:
>>>>>> +	 *
>>>>>> +	 * Threshold value for which to wait.
>>>>>> +	 */
>>>>>>  	__u32 thresh;
>>>>>> +
>>>>>> +	/**
>>>>>> +	 * @timeout:
>>>>>> +	 *
>>>>>> +	 * Timeout, in milliseconds, to wait.
>>>>>> +	 */
>>>>>>  	__u32 timeout;
>>>>>> +
>>>>>> +	/**
>>>>>> +	 * @value:
>>>>>> +	 *
>>>>>> +	 * The new syncpoint value after the wait. Set by the kernel upon
>>>>>> +	 * successful completion of the IOCTL.
>>>>>> +	 */
>>>>>>  	__u32 value;
>>>>>>  };
>>>>>>  
>>>>>>  #define DRM_TEGRA_NO_TIMEOUT	(0xffffffff)
>>>>>>  
>>>>>> +/**
>>>>>> + * struct drm_tegra_open_channel - parameters for the open channel IOCTL
>>>>>> + */
>>>>>>  struct drm_tegra_open_channel {
>>>>>> +	/**
>>>>>> +	 * @client:
>>>>>> +	 *
>>>>>> +	 * The client ID for this channel.
>>>>>> +	 */
>>>>>>  	__u32 client;
>>>>>> +
>>>>>> +	/**
>>>>>> +	 * @pad:
>>>>>> +	 *
>>>>>> +	 * Structure padding that may be used in the future. Must be 0.
>>>>>> +	 */
>>>>>>  	__u32 pad;
>>>>>> +
>>>>>> +	/**
>>>>>> +	 * @context:
>>>>>> +	 *
>>>>>> +	 * The application context of this channel. Set by the kernel upon
>>>>>> +	 * successful completion of the IOCTL. This context needs to be passed
>>>>>> +	 * to the DRM_TEGRA_CHANNEL_CLOSE or the DRM_TEGRA_SUBMIT IOCTLs.
>>>>>> +	 */
>>>>>>  	__u64 context;
>>>>>>  };
>>>>>>  
>>>>>> +/**
>>>>>> + * struct drm_tegra_close_channel - parameters for the close channel IOCTL
>>>>>> + */
>>>>>>  struct drm_tegra_close_channel {
>>>>>> +	/**
>>>>>> +	 * @context:
>>>>>> +	 *
>>>>>> +	 * The application context of this channel. This is obtained from the
>>>>>> +	 * DRM_TEGRA_OPEN_CHANNEL IOCTL.
>>>>>> +	 */
>>>>>>  	__u64 context;
>>>>>>  };
>>>>>>  
>>>>>> +/**
>>>>>> + * struct drm_tegra_get_syncpt - parameters for the get syncpoint IOCTL
>>>>>> + */
>>>>>>  struct drm_tegra_get_syncpt {
>>>>>> +	/**
>>>>>> +	 * @context:
>>>>>> +	 *
>>>>>> +	 * The application context identifying the channel for which to obtain
>>>>>> +	 * the syncpoint ID.
>>>>>> +	 */
>>>>>>  	__u64 context;
>>>>>> +
>>>>>> +	/**
>>>>>> +	 * @index:
>>>>>> +	 *
>>>>>> +	 * Index of the client syncpoint for which to obtain the ID.
>>>>>> +	 */
>>>>>>  	__u32 index;
>>>>>> +
>>>>>> +	/**
>>>>>> +	 * @id:
>>>>>> +	 *
>>>>>> +	 * The ID of the given syncpoint. Set by the kernel upon successful
>>>>>> +	 * completion of the IOCTL.
>>>>>> +	 */
>>>>>>  	__u32 id;
>>>>>>  };
>>>>>>  
>>>>>> +/**
>>>>>> + * struct drm_tegra_get_syncpt_base - parameters for the get wait base IOCTL
>>>>>> + */
>>>>>>  struct drm_tegra_get_syncpt_base {
>>>>>> +	/**
>>>>>> +	 * @context:
>>>>>> +	 *
>>>>>> +	 * The application context identifying for which channel to obtain the
>>>>>> +	 * wait base.
>>>>>> +	 */
>>>>>>  	__u64 context;
>>>>>> +
>>>>>> +	/**
>>>>>> +	 * @syncpt:
>>>>>> +	 *
>>>>>> +	 * ID of the syncpoint for which to obtain the wait base.
>>>>>> +	 */
>>>>>>  	__u32 syncpt;
>>>>>> +
>>>>>> +	/**
>>>>>> +	 * @id:
>>>>>> +	 *
>>>>>> +	 * The ID of the wait base corresponding to the client syncpoint. Set
>>>>>> +	 * by the kernel upon successful completion of the IOCTL.
>>>>>> +	 */
>>>>>>  	__u32 id;
>>>>>>  };
>>>>>>  
>>>>>> +/**
>>>>>> + * struct drm_tegra_syncpt - syncpoint increment operation
>>>>>> + */
>>>>>>  struct drm_tegra_syncpt {
>>>>>> +	/**
>>>>>> +	 * @id:
>>>>>> +	 *
>>>>>> +	 * ID of the syncpoint to operate on.
>>>>>> +	 */
>>>>>>  	__u32 id;
>>>>>> +
>>>>>> +	/**
>>>>>> +	 * @incrs:
>>>>>> +	 *
>>>>>> +	 * Number of increments to perform for the syncpoint.
>>>>>> +	 */
>>>>>>  	__u32 incrs;
>>>>>>  };
>>>>>>  
>>>>>> +/**
>>>>>> + * struct drm_tegra_cmdbuf - structure describing a command buffer
>>>>>> + */
>>>>>>  struct drm_tegra_cmdbuf {
>>>>>> +	/**
>>>>>> +	 * @handle:
>>>>>> +	 *
>>>>>> +	 * Handle to a GEM object containing the command buffer.
>>>>>> +	 */
>>>>>>  	__u32 handle;
>>>>>> +
>>>>>> +	/**
>>>>>> +	 * @offset:
>>>>>> +	 *
>>>>>> +	 * Offset, in bytes, into the GEM object identified by @handle at
>>>>>> +	 * which the command buffer starts.
>>>>>> +	 */
>>>>>>  	__u32 offset;
>>>>>> +
>>>>>> +	/**
>>>>>> +	 * @words:
>>>>>> +	 *
>>>>>> +	 * Number of 32-bit words in this command buffer.
>>>>>> +	 */
>>>>>>  	__u32 words;
>>>>>> +
>>>>>> +	/**
>>>>>> +	 * @pad:
>>>>>> +	 *
>>>>>> +	 * Structure padding that may be used in the future. Must be 0.
>>>>>> +	 */
>>>>>>  	__u32 pad;
>>>>>>  };
>>>>>>  
>>>>>> +/**
>>>>>> + * struct drm_tegra_reloc - GEM object relocation structure
>>>>>> + */
>>>>>>  struct drm_tegra_reloc {
>>>>>>  	struct {
>>>>>> +		/**
>>>>>> +		 * @cmdbuf.handle:
>>>>>> +		 *
>>>>>> +		 * Handle to the GEM object containing the command buffer for
>>>>>> +		 * which to perform this GEM object relocation.
>>>>>> +		 */
>>>>>>  		__u32 handle;
>>>>>> +
>>>>>> +		/**
>>>>>> +		 * @cmdbuf.offset:
>>>>>> +		 *
>>>>>> +		 * Offset, in bytes, into the command buffer at which to
>>>>>> +		 * insert the relocated address.
>>>>>> +		 */
>>>>>>  		__u32 offset;
>>>>>>  	} cmdbuf;
>>>>>>  	struct {
>>>>>> +		/**
>>>>>> +		 * @target.handle:
>>>>>> +		 *
>>>>>> +		 * Handle to the GEM object to be relocated.
>>>>>> +		 */
>>>>>>  		__u32 handle;
>>>>>> +
>>>>>> +		/**
>>>>>> +		 * @target.offset:
>>>>>> +		 *
>>>>>> +		 * Offset, in bytes, into the target GEM object at which the
>>>>>> +		 * relocated data starts.
>>>>>> +		 */
>>>>>>  		__u32 offset;
>>>>>>  	} target;
>>>>>> +
>>>>>> +	/**
>>>>>> +	 * @shift:
>>>>>> +	 *
>>>>>> +	 * The number of bits by which to shift relocated addresses.
>>>>>> +	 */
>>>>>>  	__u32 shift;
>>>>>> +
>>>>>> +	/**
>>>>>> +	 * @pad:
>>>>>> +	 *
>>>>>> +	 * Structure padding that may be used in the future. Must be 0.
>>>>>> +	 */
>>>>>>  	__u32 pad;
>>>>>>  };
>>>>>>  
>>>>>> +/**
>>>>>> + * struct drm_tegra_waitchk - wait check structure
>>>>>> + */
>>>>>>  struct drm_tegra_waitchk {
>>>>>> +	/**
>>>>>> +	 * @handle:
>>>>>> +	 *
>>>>>> +	 * Handle to the GEM object containing a command stream on which to
>>>>>> +	 * perform the wait check.
>>>>>> +	 */
>>>>>>  	__u32 handle;
>>>>>> +
>>>>>> +	/**
>>>>>> +	 * @offset:
>>>>>> +	 *
>>>>>> +	 * Offset, in bytes, of the location in the command stream to perform
>>>>>> +	 * the wait check on.
>>>>>> +	 */
>>>>>>  	__u32 offset;
>>>>>> +
>>>>>> +	/**
>>>>>> +	 * @syncpt:
>>>>>> +	 *
>>>>>> +	 * ID of the syncpoint to wait check.
>>>>>> +	 */
>>>>>>  	__u32 syncpt;
>>>>>> +
>>>>>> +	/**
>>>>>> +	 * @thresh:
>>>>>> +	 *
>>>>>> +	 * Threshold value for which to check.
>>>>>> +	 */
>>>>>>  	__u32 thresh;
>>>>>>  };
>>>>>>  
>>>>>> +/**
>>>>>> + * struct drm_tegra_submit - job submission structure
>>>>>> + */
>>>>>>  struct drm_tegra_submit {
>>>>>> +	/**
>>>>>> +	 * @context:
>>>>>> +	 *
>>>>>> +	 * The application context identifying the channel to use for the
>>>>>> +	 * execution of this job.
>>>>>> +	 */
>>>>>>  	__u64 context;
>>>>>> +
>>>>>> +	/**
>>>>>> +	 * @num_syncpts:
>>>>>> +	 *
>>>>>> +	 * The number of syncpoints operated on by this job.
>>>>>> +	 */
>>>>>>  	__u32 num_syncpts;
>>>>>> +
>>>>>> +	/**
>>>>>> +	 * @num_cmdbufs:
>>>>>> +	 *
>>>>>> +	 * The number of command buffers to execute as part of this job.
>>>>>> +	 */
>>>>>>  	__u32 num_cmdbufs;
>>>>>> +
>>>>>> +	/**
>>>>>> +	 * @num_relocs:
>>>>>> +	 *
>>>>>> +	 * The number of relocations to perform before executing this job.
>>>>>> +	 */
>>>>>>  	__u32 num_relocs;
>>>>>> +
>>>>>> +	/**
>>>>>> +	 * @num_waitchks:
>>>>>> +	 *
>>>>>> +	 * The number of wait checks to perform as part of this job.
>>>>>> +	 */
>>>>>>  	__u32 num_waitchks;
>>>>>> +
>>>>>> +	/**
>>>>>> +	 * @waitchk_mask:
>>>>>> +	 *
>>>>>> +	 * Bitmask of valid wait checks.
>>>>>> +	 */
>>>>>>  	__u32 waitchk_mask;
>>>>>> +
>>>>>> +	/**
>>>>>> +	 * @timeout:
>>>>>> +	 *
>>>>>> +	 * Timeout, in milliseconds, before this job is cancelled.
>>>>>> +	 */
>>>>>>  	__u32 timeout;
>>>>>> +
>>>>>> +	/**
>>>>>> +	 * @syncpts:
>>>>>> +	 *
>>>>>> +	 * A pointer to @num_syncpts &struct drm_tegra_syncpt structures that
>>>>>
>>>>> I'm not sure whether this "pointer to @num_syncpts" makes sense, shouldn't it be:
>>>>>
>>>>> 	A pointer to &struct drm_tegra_syncpt structures that...
>>>>>
>>>>> ?
>>>>>
>>>>> Same for the @cmdbufs/@relocs/@waitchks members.
>>>>
>>>> I wanted to have the references to those fields in the text so that it
>>>> becomes obvious that num_syncpts defines the number of entries in this
>>>> syncpts array.
>>>>
>>>> Perhaps a better formulation would be:
>>>>
>>>> 	A pointer to an array of @num_syncpts &struct drm_tegra_syncpt
>>>> 	structure that...
>>>>
>>>> ?
>>
>> That variant is good to me.
>>
>>>
>>> Another alternative may be:
>>>
>>> 	/**
>>> 	 * @syncpts:
>>> 	 *
>>> 	 * A pointer to an array of &struct drm_tegra_syncpt structure that
>>> 	 * specify the syncpoint operations performed as part of this job.
>>> 	 * The number of elements in the array must be equal to the value
>>> 	 * given by @num_syncpts.
>>> 	 */
>>>
>>> That's slightly easier to read but also very explicit in relating both
>>> fields to one another. Perhaps a two-way link can be established by
>>> adding something like this to the description of @num_syncpts:
>>>
>>> 	/**
>>> 	 * @num_syncpts:
>>> 	 *
>>> 	 * The number of syncpoints operated on by this job. This defines
>>> 	 * the length of the array pointed to by @syncpts.
>>> 	 */
>>
>> But this variant is even better.
>>
>> I don't mind either way, choose what you prefer.
> 
> I went with the latter. I've updated all of these field descriptions and
> added your Reviewed-by. Pushed everything to drm/tegra/for-next and will
> send a pull request for that branch shortly.

Awesome! I think Mikko was going to make a patch to the validation bug in the
submit code that he spotted recently, so maybe it would worth to postpone the
pull request a tad.
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