Re: [PATCH v3 1/7] drm: Add common fdinfo helper

[Daniel Vetter <daniel@ffwll.ch>]

On Tue, Apr 11, 2023 at 03:56:06PM -0700, Rob Clark wrote:
> From: Rob Clark <robdclark@chromium.org>
> 
> Handle a bit of the boiler-plate in a single case, and make it easier to
> add some core tracked stats.
> 
> Signed-off-by: Rob Clark <robdclark@chromium.org>

Thanks a lot for kicking this off. A few polish comments below, with those
addressed:

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

> ---
>  drivers/gpu/drm/drm_file.c | 39 ++++++++++++++++++++++++++++++++++++++
>  include/drm/drm_drv.h      |  7 +++++++
>  include/drm/drm_file.h     |  4 ++++
>  3 files changed, 50 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c
> index a51ff8cee049..37dfaa6be560 100644
> --- a/drivers/gpu/drm/drm_file.c
> +++ b/drivers/gpu/drm/drm_file.c
> @@ -148,6 +148,7 @@ bool drm_dev_needs_global_mutex(struct drm_device *dev)
>   */
>  struct drm_file *drm_file_alloc(struct drm_minor *minor)
>  {
> +	static atomic_t ident = ATOMIC_INIT(0);

Maybe make this atomic64_t just to be sure?

>  	struct drm_device *dev = minor->dev;
>  	struct drm_file *file;
>  	int ret;
> @@ -156,6 +157,8 @@ struct drm_file *drm_file_alloc(struct drm_minor *minor)
>  	if (!file)
>  		return ERR_PTR(-ENOMEM);
>  
> +	/* Get a unique identifier for fdinfo: */
> +	file->client_id = atomic_inc_return(&ident) - 1;
>  	file->pid = get_pid(task_pid(current));
>  	file->minor = minor;
>  
> @@ -868,6 +871,42 @@ void drm_send_event(struct drm_device *dev, struct drm_pending_event *e)
>  }
>  EXPORT_SYMBOL(drm_send_event);
>  
> +/**
> + * drm_fop_show_fdinfo - helper for drm file fops
> + * @seq_file: output stream
> + * @f: the device file instance
> + *
> + * Helper to implement fdinfo, for userspace to query usage stats, etc, of a
> + * process using the GPU.

Please mention drm_driver.show_fd_info here too.

> + */
> +void drm_fop_show_fdinfo(struct seq_file *m, struct file *f)
> +{
> +	struct drm_file *file = f->private_data;
> +	struct drm_device *dev = file->minor->dev;
> +	struct drm_printer p = drm_seq_file_printer(m);
> +
> +	/*
> +	 * ******************************************************************
> +	 * For text output format description please see drm-usage-stats.rst!
> +	 * ******************************************************************

Maybe move this into the kerneldoc comment above (perhaps with an
IMPORTANT: tag or something, and make it an actual link)?

Also in the drm-usage-stats.rst please put a link to this function and
that is must be used for implementing fd_info.

> +	 */
> +
> +	drm_printf(&p, "drm-driver:\t%s\n", dev->driver->name);
> +	drm_printf(&p, "drm-client-id:\t%u\n", file->client_id);
> +
> +	if (dev_is_pci(dev->dev)) {
> +		struct pci_dev *pdev = to_pci_dev(dev->dev);
> +
> +		drm_printf(&p, "drm-pdev:\t%04x:%02x:%02x.%d\n",
> +			   pci_domain_nr(pdev->bus), pdev->bus->number,
> +			   PCI_SLOT(pdev->devfn), PCI_FUNC(pdev->devfn));
> +	}
> +
> +	if (dev->driver->show_fdinfo)
> +		dev->driver->show_fdinfo(&p, file);
> +}
> +EXPORT_SYMBOL(drm_fop_show_fdinfo);

Bit a bikeshed, but for consistency drop the _fop_? We don't have it for
any of the other drm fops and git grep doesn't show a naming conflict.

> +
>  /**
>   * mock_drm_getfile - Create a new struct file for the drm device
>   * @minor: drm minor to wrap (e.g. #drm_device.primary)
> diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h
> index 5b86bb7603e7..a883c6d3bcdf 100644
> --- a/include/drm/drm_drv.h
> +++ b/include/drm/drm_drv.h
> @@ -401,6 +401,13 @@ struct drm_driver {
>  			       struct drm_device *dev, uint32_t handle,
>  			       uint64_t *offset);
>  
> +	/**
> +	 * @fdinfo:
> +	 *
> +	 * Print device specific fdinfo.  See drm-usage-stats.rst.

Please make this a link. I like links in kerneldoc :-)

> +	 */
> +	void (*show_fdinfo)(struct drm_printer *p, struct drm_file *f);
> +
>  	/** @major: driver major number */
>  	int major;
>  	/** @minor: driver minor number */
> diff --git a/include/drm/drm_file.h b/include/drm/drm_file.h
> index 0d1f853092ab..dfa995b787e1 100644
> --- a/include/drm/drm_file.h
> +++ b/include/drm/drm_file.h
> @@ -258,6 +258,9 @@ struct drm_file {
>  	/** @pid: Process that opened this file. */
>  	struct pid *pid;
>  
> +	/** @client_id: A unique id for fdinfo */
> +	u32 client_id;
> +
>  	/** @magic: Authentication magic, see @authenticated. */
>  	drm_magic_t magic;
>  
> @@ -437,6 +440,7 @@ void drm_send_event(struct drm_device *dev, struct drm_pending_event *e);
>  void drm_send_event_timestamp_locked(struct drm_device *dev,
>  				     struct drm_pending_event *e,
>  				     ktime_t timestamp);
> +void drm_fop_show_fdinfo(struct seq_file *m, struct file *f);
>  
>  struct file *mock_drm_getfile(struct drm_minor *minor, unsigned int flags);
>  
> -- 
> 2.39.2
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch