On Wed, Apr 06, 2022 at 11:39:16PM +0200, Javier Martinez Canillas wrote:
> These can be used by subsystems to unregister a platform device registered
> by sysfb and also to disable future platform device registration in sysfb.
> 
> Suggested-by: Daniel Vetter <daniel.vet...@ffwll.ch>
> Signed-off-by: Javier Martinez Canillas <javi...@redhat.com>
> ---
> 
>  drivers/firmware/sysfb.c | 47 +++++++++++++++++++++++++++++++++++-----
>  include/linux/sysfb.h    | 19 ++++++++++++++++
>  2 files changed, 60 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/firmware/sysfb.c b/drivers/firmware/sysfb.c
> index b032f40a92de..08ae78c083f1 100644
> --- a/drivers/firmware/sysfb.c
> +++ b/drivers/firmware/sysfb.c
> @@ -34,21 +34,52 @@
>  #include <linux/screen_info.h>
>  #include <linux/sysfb.h>
>  
> +static struct platform_device *pd;
> +static DEFINE_MUTEX(load_lock);
> +static bool disabled;
> +
> +void sysfb_disable(void)
> +{
> +     mutex_lock(&load_lock);
> +     disabled = true;
> +     mutex_unlock(&load_lock);
> +}
> +EXPORT_SYMBOL_GPL(sysfb_disable);
> +
> +bool sysfb_try_unregister(struct device *dev)
> +{
> +     bool ret = true;
> +
> +     mutex_lock(&load_lock);
> +     if (!pd || pd != to_platform_device(dev))
> +             return false;
> +
> +     platform_device_unregister(to_platform_device(dev));
> +     pd = NULL;
> +     mutex_unlock(&load_lock);
> +
> +     return ret;
> +}
> +EXPORT_SYMBOL_GPL(sysfb_try_unregister);

Kerneldoc for these plus adding that to
Documentation/firmware/other_interfaces.rst would be really neat.

With that added Reviewed-by: Daniel Vetter <daniel.vet...@ffwll.ch>


> +
>  static __init int sysfb_init(void)
>  {
>       struct screen_info *si = &screen_info;
>       struct simplefb_platform_data mode;
> -     struct platform_device *pd;
>       const char *name;
>       bool compatible;
> -     int ret;
> +     int ret = 0;
> +
> +     mutex_lock(&load_lock);
> +     if (disabled)
> +             goto unlock_mutex;
>  
>       /* try to create a simple-framebuffer device */
>       compatible = sysfb_parse_mode(si, &mode);
>       if (compatible) {
>               pd = sysfb_create_simplefb(si, &mode);
>               if (!IS_ERR(pd))
> -                     return 0;
> +                     goto unlock_mutex;
>       }
>  
>       /* if the FB is incompatible, create a legacy framebuffer device */
> @@ -60,8 +91,10 @@ static __init int sysfb_init(void)
>               name = "platform-framebuffer";
>  
>       pd = platform_device_alloc(name, 0);
> -     if (!pd)
> -             return -ENOMEM;
> +     if (!pd) {
> +             ret = -ENOMEM;
> +             goto unlock_mutex;
> +     }
>  
>       sysfb_apply_efi_quirks(pd);
>  
> @@ -73,9 +106,11 @@ static __init int sysfb_init(void)
>       if (ret)
>               goto err;
>  
> -     return 0;
> +     goto unlock_mutex;
>  err:
>       platform_device_put(pd);
> +unlock_mutex:
> +     mutex_unlock(&load_lock);
>       return ret;
>  }
>  
> diff --git a/include/linux/sysfb.h b/include/linux/sysfb.h
> index 708152e9037b..e8c0313fac8f 100644
> --- a/include/linux/sysfb.h
> +++ b/include/linux/sysfb.h
> @@ -55,6 +55,25 @@ struct efifb_dmi_info {
>       int flags;
>  };
>  
> +#ifdef CONFIG_SYSFB
> +
> +void sysfb_disable(void);
> +bool sysfb_try_unregister(struct device *dev);
> +
> +#else /* CONFIG_SYSFB */
> +
> +static inline void sysfb_disable(void)
> +{
> +
> +}
> +
> +static inline bool sysfb_try_unregister(struct device *dev)
> +{
> +     return false;
> +}
> +
> +#endif /* CONFIG_SYSFB */
> +
>  #ifdef CONFIG_EFI
>  
>  extern struct efifb_dmi_info efifb_dmi_list[];
> -- 
> 2.35.1
> 

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

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