Re: [PATCH 4/9] drm/verisilicon: Add gem driver for JH7110 SoC

[Thomas Zimmermann]

Hi

Am 19.06.23 um 16:22 schrieb Thomas Zimmermann:
> Hi
>
> Am 02.06.23 um 09:40 schrieb Keith Zhao:
> > This patch implements gem related APIs for JH7100 SoC.
>
> please also see my other reply to this patch. My mail client had a bug 
> before I could finish it. Below are some more comments.
>
> > Signed-off-by: Keith Zhao <keith.zhao@xxxxxxxxxxxxxxxx>
> > ---
> [...]
> > +#ifndef __VS_GEM_H__
> > +#define __VS_GEM_H__
> > +
> > +#include <linux/dma-buf.h>
> > +
> > +#include <drm/drm_gem.h>
> > +#include <drm/drm_prime.h>
> > +
> > +#include "vs_drv.h"
> > +/*
> > + *
> > + * @base: drm gem object.
> > + * @size: size requested from user
> > + * @cookie: cookie returned by dma_alloc_attrs
> > + *    - not kernel virtual address with DMA_ATTR_NO_KERNEL_MAPPING
> > + * @dma_addr: bus address(accessed by dma) to allocated memory region.
> > + *    - this address could be physical address without IOMMU and
> > + *    device address with IOMMU.
> > + * @dma_attrs: attribute for DMA API
> > + * @get_pages: flag for manually applying for non-contiguous memory.
> > + * @pages: Array of backing pages.
> > + * @sgt: Imported sg_table.
> > + *
> > + */
> > +struct vs_gem_object {
> > +    struct drm_gem_object    base;
> > +    size_t            size;
> > +    void            *cookie;
> > +    dma_addr_t        dma_addr;
> > +    u32                iova;
> > +    unsigned long    dma_attrs;
> > +    bool            get_pages;
> > +    struct page        **pages;
> > +    struct sg_table *sgt;
> > +};
> > +
> > +static inline
> > +struct vs_gem_object *to_vs_gem_object(struct drm_gem_object *obj)
> > +{
> > +    return container_of(obj, struct vs_gem_object, base);
> > +}
> > +
> > +struct vs_gem_object *vs_gem_create_object(struct drm_device *dev,
> > +                       size_t size);
> > +
> > +int vs_gem_prime_vmap(struct drm_gem_object *obj, struct iosys_map 
> > *map);
> > +void vs_gem_prime_vunmap(struct drm_gem_object *obj, struct iosys_map 
> > *map);
>
> I'd consider this bad style. Your functions are in the vs_ namespace, so 
> they should take a vs_gem_object as first argument. Rather implement 
> vs_gem_prime_vmap(struct vs_gem_object *vs_obj, struct iosys_map *map)
> and _vunmap() and _mmap().
>
> For the callbacks in struct drm_gemobject_funcs, you can write small 
> wrappers around the helpers to do the type casting. See 
> drm_gem_shmem_object_mmap() and drm_gem_shmem_mmap() for an example.
>
> https://elixir.bootlin.com/linux/latest/source/include/drm/drm_gem_shmem_helper.h#L233

I was thinking about my advise with the wrappers, but it doesn't seem so 
good after all. Maybe just ignore it. I think you should still rename 
the function to something like vs_gem_object_vmap(), etc.  So they name 
reflects that they operate on a struct drm_gem_object.

But many of the helpers in this file are only ever used in vs_gem.c. 
You should declare them static in the C file and remove them from this 
header.

Best regards
Thomas

> > +
> > +int vs_gem_prime_mmap(struct drm_gem_object *obj,
> > +              struct vm_area_struct *vma);
> > +
> > +int vs_gem_dumb_create(struct drm_file *file_priv,
> > +               struct drm_device *drm,
> > +               struct drm_mode_create_dumb *args);
> > +
> > +int vs_gem_mmap(struct file *filp, struct vm_area_struct *vma);
> > +
> > +struct sg_table *vs_gem_prime_get_sg_table(struct drm_gem_object *obj);
> > +
> > +struct drm_gem_object *vs_gem_prime_import(struct drm_device *dev,
> > +                       struct dma_buf *dma_buf);
> > +struct drm_gem_object *
> > +vs_gem_prime_import_sg_table(struct drm_device *dev,
> > +                 struct dma_buf_attachment *attach,
> > +                 struct sg_table *sgt);
> > +
> > +#endif /* __VS_GEM_H__ */

--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)

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