linux-kernel - Re: [PATCHv3 2/3] drm/prime: Introduce drm_gem_prime_import

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Message-ID: <20170502202213.GI19680@nuc-i3427.alporthouse.com>
Date:   Tue, 2 May 2017 21:22:13 +0100
From:   Chris Wilson <chris@...is-wilson.co.uk>
To:     Laura Abbott <labbott@...hat.com>
Cc:     Daniel Vetter <daniel.vetter@...ll.ch>,
        Sean Paul <seanpaul@...omium.org>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Sumit Semwal <sumit.semwal@...aro.org>,
        intel-gfx@...ts.freedesktop.org,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>
Subject: Re: [PATCHv3 2/3] drm/prime: Introduce drm_gem_prime_import_platform

On Tue, May 02, 2017 at 10:02:07AM -0700, Laura Abbott wrote:
> The existing drm_gem_prime_import function uses the underlying
> struct device of a drm_device for attaching to a dma_buf. Some drivers
> (notably vgem) may not have an underlying device structure. Offer
> an alternate function to attach using a platform device associated
> with drm_device.
> 
> Cc: intel-gfx@...ts.freedesktop.org
> Reviewed-by: Chris Wilson <chris@...is-wilson.co.uk>
> Signed-off-by: Laura Abbott <labbott@...hat.com>
> ---
> v3: Rebase to drm-misc-next. Prototype moved to a new header file. Comments
> added for new function. Brought back drm_device->platformdev as it had been
> removed in 76adb460fd93 ("drm: Remove the struct drm_device platformdev field").
> I'm not entirely thrilled about this since the platformdev removal was good
> cleanup and this feels like a small step backwards. I don't know of a better
> approach though.
> ---
>  drivers/gpu/drm/drm_prime.c | 49 +++++++++++++++++++++++++++++++++++----------
>  include/drm/drmP.h          |  2 ++
>  include/drm/drm_prime.h     |  4 ++++
>  3 files changed, 44 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
> index 9fb65b7..a557a4b 100644
> --- a/drivers/gpu/drm/drm_prime.c
> +++ b/drivers/gpu/drm/drm_prime.c
> @@ -594,16 +594,9 @@ int drm_gem_prime_handle_to_fd(struct drm_device *dev,
>  }
>  EXPORT_SYMBOL(drm_gem_prime_handle_to_fd);
>  
> -/**
> - * drm_gem_prime_import - helper library implementation of the import callback
> - * @dev: drm_device to import into
> - * @dma_buf: dma-buf object to import
> - *
> - * This is the implementation of the gem_prime_import functions for GEM drivers
> - * using the PRIME helpers.
> - */
> -struct drm_gem_object *drm_gem_prime_import(struct drm_device *dev,
> -					    struct dma_buf *dma_buf)
> +static struct drm_gem_object *__drm_gem_prime_import(struct drm_device *dev,
> +					    struct dma_buf *dma_buf,
> +					    struct device *attach_dev)
>  {
>  	struct dma_buf_attachment *attach;
>  	struct sg_table *sgt;
> @@ -625,7 +618,7 @@ struct drm_gem_object *drm_gem_prime_import(struct drm_device *dev,
>  	if (!dev->driver->gem_prime_import_sg_table)
>  		return ERR_PTR(-EINVAL);
>  
> -	attach = dma_buf_attach(dma_buf, dev->dev);
> +	attach = dma_buf_attach(dma_buf, attach_dev);
>  	if (IS_ERR(attach))
>  		return ERR_CAST(attach);
>  
> @@ -655,9 +648,43 @@ struct drm_gem_object *drm_gem_prime_import(struct drm_device *dev,
>  
>  	return ERR_PTR(ret);
>  }
> +
> +/**
> + * drm_gem_prime_import - helper library implementation of the import callback
> + * @dev: drm_device to import into
> + * @dma_buf: dma-buf object to import
> + *
> + * This is the implementation of the gem_prime_import functions for GEM drivers
> + * using the PRIME helpers.
> + */
> +struct drm_gem_object *drm_gem_prime_import(struct drm_device *dev,
> +					    struct dma_buf *dma_buf)
> +{
> +	return __drm_gem_prime_import(dev, dma_buf, dev->dev);
> +}
>  EXPORT_SYMBOL(drm_gem_prime_import);
>  
>  /**
> + * drm_gem_prime_import_platform - alternate implementation of the import callback
> + * @dev: drm_device to import into
> + * @dma_buf: dma-buf object to import
> + *
> + * This is identical to drm_gem_prime_import except the device used for dma_buf
> + * attachment is an internal platform device instead of the standard device
> + * structure. The use of this function should be limited to drivers that do not
> + * set up an underlying device structure.
> + */
> +struct drm_gem_object *drm_gem_prime_import_platform(struct drm_device *dev,

Simpler soluation will be for the caller to provide the platformdev?

That works nicely for the vgem case, I think.

> +					    struct dma_buf *dma_buf)
> +{
> +	if (WARN_ON_ONCE(!dev->platformdev))
> +		return NULL;
> +
> +	return __drm_gem_prime_import(dev, dma_buf, &dev->platformdev->dev);
> +}
> +EXPORT_SYMBOL(drm_gem_prime_import_platform);

-- 
Chris Wilson, Intel Open Source Technology Centre