Nouveau - Dec 2023 - [PATCH -next] drm/nouveau: uapi: fix kerneldoc warnings

As of commit b77fdd6a48e6 ("scripts/kernel-doc: restore warning for
Excess struct/union"), we see the following warnings when running 'make
htmldocs':

  ./include/uapi/drm/nouveau_drm.h:292: warning: Excess struct member
'DRM_NOUVEAU_VM_BIND_OP_MAP' description in
'drm_nouveau_vm_bind_op'
  ./include/uapi/drm/nouveau_drm.h:292: warning: Excess struct member
'DRM_NOUVEAU_VM_BIND_OP_UNMAP' description in
'drm_nouveau_vm_bind_op'
  ./include/uapi/drm/nouveau_drm.h:292: warning: Excess struct member
'DRM_NOUVEAU_VM_BIND_SPARSE' description in
'drm_nouveau_vm_bind_op'
  ./include/uapi/drm/nouveau_drm.h:336: warning: Excess struct member
'DRM_NOUVEAU_VM_BIND_RUN_ASYNC' description in
'drm_nouveau_vm_bind'

The problem is that these values are #define constants, but had kerneldoc
comments attached to them as if they were actual struct members.

There are a number of ways we could fix this, but I chose to draw
inspiration from include/uapi/drm/i915_drm.h, which pulls them into the
corresponding kerneldoc comment for the struct member that they are
intended to be used with.

To keep the diff readable, there are a number of things I _didn't_ do in
this patch, but which we should also consider:

- This is pretty good documentation, but it ends up in gpu/driver-uapi,
  which is part of subsystem-apis/ when it really ought to display under
  userspace-api/ (the "Linux kernel user-space API guide" book of the
  documentation).

- More generally, we might want a warning if include/uapi/ files are
  kerneldoc'd outside userspace-api/.

- I'd consider it cleaner if the #defines appeared between the kerneldoc
  for the member and the member itself (which is something other DRM-
  related UAPI docs do).

- The %IDENTIFIER kerneldoc syntax is intended for "constants", and is
  more appropriate in this context than ``IDENTIFIER`` or &IDENTIFIER.
  The DRM docs aren't very consistent on this.

Cc: Randy Dunlap <rdunlap at infradead.org>
Cc: Jonathan Corbet <corbet at lwn.net>
Signed-off-by: Vegard Nossum <vegard.nossum at oracle.com>
---
 include/uapi/drm/nouveau_drm.h | 56 ++++++++++++++++------------------
 1 file changed, 27 insertions(+), 29 deletions(-)

diff --git a/include/uapi/drm/nouveau_drm.h b/include/uapi/drm/nouveau_drm.h
index 0bade1592f34..c95ef8a4d94a 100644
--- a/include/uapi/drm/nouveau_drm.h
+++ b/include/uapi/drm/nouveau_drm.h
@@ -238,34 +238,32 @@ struct drm_nouveau_vm_init {
 struct drm_nouveau_vm_bind_op {
 	/**
 	 * @op: the operation type
+	 *
+	 * Supported values:
+	 *
+	 * %DRM_NOUVEAU_VM_BIND_OP_MAP - Map a GEM object to the GPU's VA
+	 * space. Optionally, the &DRM_NOUVEAU_VM_BIND_SPARSE flag can be
+	 * passed to instruct the kernel to create sparse mappings for the
+	 * given range.
+	 *
+	 * %DRM_NOUVEAU_VM_BIND_OP_UNMAP - Unmap an existing mapping in the
+	 * GPU's VA space. If the region the mapping is located in is a
+	 * sparse region, new sparse mappings are created where the unmapped
+	 * (memory backed) mapping was mapped previously. To remove a sparse
+	 * region the &DRM_NOUVEAU_VM_BIND_SPARSE must be set.
 	 */
 	__u32 op;
-/**
- * @DRM_NOUVEAU_VM_BIND_OP_MAP:
- *
- * Map a GEM object to the GPU's VA space. Optionally, the
- * &DRM_NOUVEAU_VM_BIND_SPARSE flag can be passed to instruct the kernel to
- * create sparse mappings for the given range.
- */
 #define DRM_NOUVEAU_VM_BIND_OP_MAP 0x0
-/**
- * @DRM_NOUVEAU_VM_BIND_OP_UNMAP:
- *
- * Unmap an existing mapping in the GPU's VA space. If the region the
mapping
- * is located in is a sparse region, new sparse mappings are created where the
- * unmapped (memory backed) mapping was mapped previously. To remove a sparse
- * region the &DRM_NOUVEAU_VM_BIND_SPARSE must be set.
- */
 #define DRM_NOUVEAU_VM_BIND_OP_UNMAP 0x1
 	/**
 	 * @flags: the flags for a &drm_nouveau_vm_bind_op
+	 *
+	 * Supported values:
+	 *
+	 * %DRM_NOUVEAU_VM_BIND_SPARSE - Indicates that an allocated VA
+	 * space region should be sparse.
 	 */
 	__u32 flags;
-/**
- * @DRM_NOUVEAU_VM_BIND_SPARSE:
- *
- * Indicates that an allocated VA space region should be sparse.
- */
 #define DRM_NOUVEAU_VM_BIND_SPARSE (1 << 8)
 	/**
 	 * @handle: the handle of the DRM GEM object to map
@@ -301,17 +299,17 @@ struct drm_nouveau_vm_bind {
 	__u32 op_count;
 	/**
 	 * @flags: the flags for a &drm_nouveau_vm_bind ioctl
+	 *
+	 * Supported values:
+	 *
+	 * %DRM_NOUVEAU_VM_BIND_RUN_ASYNC - Indicates that the given VM_BIND
+	 * operation should be executed asynchronously by the kernel.
+	 *
+	 * If this flag is not supplied the kernel executes the associated
+	 * operations synchronously and doesn't accept any &drm_nouveau_sync
+	 * objects.
 	 */
 	__u32 flags;
-/**
- * @DRM_NOUVEAU_VM_BIND_RUN_ASYNC:
- *
- * Indicates that the given VM_BIND operation should be executed asynchronously
- * by the kernel.
- *
- * If this flag is not supplied the kernel executes the associated operations
- * synchronously and doesn't accept any &drm_nouveau_sync objects.
- */
 #define DRM_NOUVEAU_VM_BIND_RUN_ASYNC 0x1
 	/**
 	 * @wait_count: the number of wait &drm_nouveau_syncs
-- 
2.34.1

On 12/24/23 22:51, Vegard Nossum wrote:
> As of commit b77fdd6a48e6 ("scripts/kernel-doc: restore warning for
> Excess struct/union"), we see the following warnings when running
'make
> htmldocs':
> 
>   ./include/uapi/drm/nouveau_drm.h:292: warning: Excess struct member
'DRM_NOUVEAU_VM_BIND_OP_MAP' description in
'drm_nouveau_vm_bind_op'
>   ./include/uapi/drm/nouveau_drm.h:292: warning: Excess struct member
'DRM_NOUVEAU_VM_BIND_OP_UNMAP' description in
'drm_nouveau_vm_bind_op'
>   ./include/uapi/drm/nouveau_drm.h:292: warning: Excess struct member
'DRM_NOUVEAU_VM_BIND_SPARSE' description in
'drm_nouveau_vm_bind_op'
>   ./include/uapi/drm/nouveau_drm.h:336: warning: Excess struct member
'DRM_NOUVEAU_VM_BIND_RUN_ASYNC' description in
'drm_nouveau_vm_bind'
> 
> The problem is that these values are #define constants, but had kerneldoc
> comments attached to them as if they were actual struct members.
> 
> There are a number of ways we could fix this, but I chose to draw
> inspiration from include/uapi/drm/i915_drm.h, which pulls them into the
> corresponding kerneldoc comment for the struct member that they are
> intended to be used with.
> 
> To keep the diff readable, there are a number of things I _didn't_ do
in
> this patch, but which we should also consider:
> 
> - This is pretty good documentation, but it ends up in gpu/driver-uapi,
>   which is part of subsystem-apis/ when it really ought to display under
>   userspace-api/ (the "Linux kernel user-space API guide" book of
the
>   documentation).
> 
> - More generally, we might want a warning if include/uapi/ files are
>   kerneldoc'd outside userspace-api/.
> 
> - I'd consider it cleaner if the #defines appeared between the
kerneldoc
>   for the member and the member itself (which is something other DRM-
>   related UAPI docs do).
> 
> - The %IDENTIFIER kerneldoc syntax is intended for "constants",
and is
>   more appropriate in this context than ``IDENTIFIER`` or &IDENTIFIER.
>   The DRM docs aren't very consistent on this.
> 
> Cc: Randy Dunlap <rdunlap at infradead.org>
> Cc: Jonathan Corbet <corbet at lwn.net>
> Signed-off-by: Vegard Nossum <vegard.nossum at oracle.com>

This all looks good to me. Thanks for your help.

Reviewed-by: Randy Dunlap <rdunlap at infradead.org>
Tested-by: Randy Dunlap <rdunlap at infradead.org>

I do see one thing that I don't like in the generated html output.
It's not a problem with this patch.
The #defines for DRM_NOUVEAU_VM_BIND_OP_MAP etc. have a ';' at the
end of each line:

struct drm_nouveau_vm_bind_op {
    __u32 op;
#define DRM_NOUVEAU_VM_BIND_OP_MAP 0x0;
#define DRM_NOUVEAU_VM_BIND_OP_UNMAP 0x1;
    __u32 flags;
#define DRM_NOUVEAU_VM_BIND_SPARSE (1 << 8);
    __u32 handle;
    __u32 pad;
    __u64 addr;
    __u64 bo_offset;
    __u64 range;
};

so something else to look into one of these days....

> ---
>  include/uapi/drm/nouveau_drm.h | 56 ++++++++++++++++------------------
>  1 file changed, 27 insertions(+), 29 deletions(-)
> 
> diff --git a/include/uapi/drm/nouveau_drm.h
b/include/uapi/drm/nouveau_drm.h
> index 0bade1592f34..c95ef8a4d94a 100644

-- 
#Randy
https://people.kernel.org/tglx/notes-about-netiquette
https://subspace.kernel.org/etiquette.html

On 12/25/23 07:51, Vegard Nossum wrote:
> As of commit b77fdd6a48e6 ("scripts/kernel-doc: restore warning for
> Excess struct/union"), we see the following warnings when running
'make
> htmldocs':
> 
>    ./include/uapi/drm/nouveau_drm.h:292: warning: Excess struct member
'DRM_NOUVEAU_VM_BIND_OP_MAP' description in
'drm_nouveau_vm_bind_op'
>    ./include/uapi/drm/nouveau_drm.h:292: warning: Excess struct member
'DRM_NOUVEAU_VM_BIND_OP_UNMAP' description in
'drm_nouveau_vm_bind_op'
>    ./include/uapi/drm/nouveau_drm.h:292: warning: Excess struct member
'DRM_NOUVEAU_VM_BIND_SPARSE' description in
'drm_nouveau_vm_bind_op'
>    ./include/uapi/drm/nouveau_drm.h:336: warning: Excess struct member
'DRM_NOUVEAU_VM_BIND_RUN_ASYNC' description in
'drm_nouveau_vm_bind'
> 
> The problem is that these values are #define constants, but had kerneldoc
> comments attached to them as if they were actual struct members.
> 
> There are a number of ways we could fix this, but I chose to draw
> inspiration from include/uapi/drm/i915_drm.h, which pulls them into the
> corresponding kerneldoc comment for the struct member that they are
> intended to be used with.
> 
> To keep the diff readable, there are a number of things I _didn't_ do
in
> this patch, but which we should also consider:
> 
> - This is pretty good documentation, but it ends up in gpu/driver-uapi,
>    which is part of subsystem-apis/ when it really ought to display under
>    userspace-api/ (the "Linux kernel user-space API guide" book
of the
>    documentation).
I agree, it indeed looks like this would make sense, same goes for
gpu/drm-uapi.rst.

@Jani, Sima: Was this intentional? Or can we change it?
> 
> - More generally, we might want a warning if include/uapi/ files are
>    kerneldoc'd outside userspace-api/.
> 
> - I'd consider it cleaner if the #defines appeared between the
kerneldoc
>    for the member and the member itself (which is something other DRM-
>    related UAPI docs do).
> 
> - The %IDENTIFIER kerneldoc syntax is intended for "constants",
and is
>    more appropriate in this context than ``IDENTIFIER`` or &IDENTIFIER.
>    The DRM docs aren't very consistent on this.
> 
> Cc: Randy Dunlap <rdunlap at infradead.org>
> Cc: Jonathan Corbet <corbet at lwn.net>
> Signed-off-by: Vegard Nossum <vegard.nossum at oracle.com>
Applied to drm-misc-next, thanks!
> ---
>   include/uapi/drm/nouveau_drm.h | 56 ++++++++++++++++------------------
>   1 file changed, 27 insertions(+), 29 deletions(-)
> 
> diff --git a/include/uapi/drm/nouveau_drm.h
b/include/uapi/drm/nouveau_drm.h
> index 0bade1592f34..c95ef8a4d94a 100644
> --- a/include/uapi/drm/nouveau_drm.h
> +++ b/include/uapi/drm/nouveau_drm.h
> @@ -238,34 +238,32 @@ struct drm_nouveau_vm_init {
>   struct drm_nouveau_vm_bind_op {
>   	/**
>   	 * @op: the operation type
> +	 *
> +	 * Supported values:
> +	 *
> +	 * %DRM_NOUVEAU_VM_BIND_OP_MAP - Map a GEM object to the GPU's VA
> +	 * space. Optionally, the &DRM_NOUVEAU_VM_BIND_SPARSE flag can be
> +	 * passed to instruct the kernel to create sparse mappings for the
> +	 * given range.
> +	 *
> +	 * %DRM_NOUVEAU_VM_BIND_OP_UNMAP - Unmap an existing mapping in the
> +	 * GPU's VA space. If the region the mapping is located in is a
> +	 * sparse region, new sparse mappings are created where the unmapped
> +	 * (memory backed) mapping was mapped previously. To remove a sparse
> +	 * region the &DRM_NOUVEAU_VM_BIND_SPARSE must be set.
>   	 */
>   	__u32 op;
> -/**
> - * @DRM_NOUVEAU_VM_BIND_OP_MAP:
> - *
> - * Map a GEM object to the GPU's VA space. Optionally, the
> - * &DRM_NOUVEAU_VM_BIND_SPARSE flag can be passed to instruct the
kernel to
> - * create sparse mappings for the given range.
> - */
>   #define DRM_NOUVEAU_VM_BIND_OP_MAP 0x0
> -/**
> - * @DRM_NOUVEAU_VM_BIND_OP_UNMAP:
> - *
> - * Unmap an existing mapping in the GPU's VA space. If the region the
mapping
> - * is located in is a sparse region, new sparse mappings are created where
the
> - * unmapped (memory backed) mapping was mapped previously. To remove a
sparse
> - * region the &DRM_NOUVEAU_VM_BIND_SPARSE must be set.
> - */
>   #define DRM_NOUVEAU_VM_BIND_OP_UNMAP 0x1
>   	/**
>   	 * @flags: the flags for a &drm_nouveau_vm_bind_op
> +	 *
> +	 * Supported values:
> +	 *
> +	 * %DRM_NOUVEAU_VM_BIND_SPARSE - Indicates that an allocated VA
> +	 * space region should be sparse.
>   	 */
>   	__u32 flags;
> -/**
> - * @DRM_NOUVEAU_VM_BIND_SPARSE:
> - *
> - * Indicates that an allocated VA space region should be sparse.
> - */
>   #define DRM_NOUVEAU_VM_BIND_SPARSE (1 << 8)
>   	/**
>   	 * @handle: the handle of the DRM GEM object to map
> @@ -301,17 +299,17 @@ struct drm_nouveau_vm_bind {
>   	__u32 op_count;
>   	/**
>   	 * @flags: the flags for a &drm_nouveau_vm_bind ioctl
> +	 *
> +	 * Supported values:
> +	 *
> +	 * %DRM_NOUVEAU_VM_BIND_RUN_ASYNC - Indicates that the given VM_BIND
> +	 * operation should be executed asynchronously by the kernel.
> +	 *
> +	 * If this flag is not supplied the kernel executes the associated
> +	 * operations synchronously and doesn't accept any
&drm_nouveau_sync
> +	 * objects.
>   	 */
>   	__u32 flags;
> -/**
> - * @DRM_NOUVEAU_VM_BIND_RUN_ASYNC:
> - *
> - * Indicates that the given VM_BIND operation should be executed
asynchronously
> - * by the kernel.
> - *
> - * If this flag is not supplied the kernel executes the associated
operations
> - * synchronously and doesn't accept any &drm_nouveau_sync objects.
> - */
>   #define DRM_NOUVEAU_VM_BIND_RUN_ASYNC 0x1
>   	/**
>   	 * @wait_count: the number of wait &drm_nouveau_syncs