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

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Message-ID: <5b87fb5c-2f23-47c9-b6a8-623472115876@suse.de>
Date:   Wed, 21 Jun 2023 12:44:28 +0200
From:   Thomas Zimmermann <tzimmermann@...e.de>
To:     Keith Zhao <keith.zhao@...rfivetech.com>,
        dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org,
        linux-media@...r.kernel.org, linaro-mm-sig@...ts.linaro.org
Cc:     Conor Dooley <conor+dt@...nel.org>,
        Albert Ou <aou@...s.berkeley.edu>,
        Emil Renner Berthing <kernel@...il.dk>,
        christian.koenig@....com, Bjorn Andersson <andersson@...nel.org>,
        Chris Morgan <macromorgan@...mail.com>,
        Changhuang Liang <changhuang.liang@...rfivetech.com>,
        Jagan Teki <jagan@...eble.ai>,
        Jack Zhu <jack.zhu@...rfivetech.com>,
        Rob Herring <robh+dt@...nel.org>,
        Palmer Dabbelt <palmer@...belt.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Shengyang Chen <shengyang.chen@...rfivetech.com>,
        Shawn Guo <shawnguo@...nel.org>,
        Sumit Semwal <sumit.semwal@...aro.org>
Subject: Re: [PATCH 4/9] drm/verisilicon: Add gem driver for JH7110 SoC

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@...rfivetech.com>
>> ---
> [...]
>> +#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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