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Date:   Fri, 21 Jul 2023 12:08:46 +0200
Message-ID: <878rb9h901.wl-tiwai@suse.de>
From:   Takashi Iwai <tiwai@suse.de>
To:     Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc:     alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org,
        Jaroslav Kysela <perex@perex.cz>,
        Takashi Iwai <tiwai@suse.com>,
        Dan Williams <dan.j.williams@intel.com>
Subject: Re: [PATCH v1 1/1] ALSA: korg1212: Re-use sockptr_t and respective APIs
In-Reply-To: <20230721100146.67293-1-andriy.shevchenko@linux.intel.com>
References: <20230721100146.67293-1-andriy.shevchenko@linux.intel.com>
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On Fri, 21 Jul 2023 12:01:46 +0200,
Andy Shevchenko wrote:
> 
> The sockptr_t (despite the naming) is a generic type to hold kernel
> or user pointer and there are respective APIs to copy data to or
> from it. Replace open coded variants in the driver by them.

While I see the benefit, I feel this is very confusing.  If we use the
API for a generic use, it should be renamed at first.

Also, the current function actually follows the call pattern, and we
know in the caller side whether it's called for a kernel pointer or a
user pointer.  So, if any, the PCM core callbacks should be revised to
use a generic pointer instead of fiddling in each driver side.


thanks,

Takashi

> 
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> ---
>  sound/pci/korg1212/korg1212.c | 33 +++++++++++++--------------------
>  1 file changed, 13 insertions(+), 20 deletions(-)
> 
> diff --git a/sound/pci/korg1212/korg1212.c b/sound/pci/korg1212/korg1212.c
> index 33b4f95d65b3..92c3eab4d12c 100644
> --- a/sound/pci/korg1212/korg1212.c
> +++ b/sound/pci/korg1212/korg1212.c
> @@ -10,6 +10,7 @@
>  #include <linux/interrupt.h>
>  #include <linux/pci.h>
>  #include <linux/slab.h>
> +#include <linux/sockptr.h>
>  #include <linux/wait.h>
>  #include <linux/module.h>
>  #include <linux/mutex.h>
> @@ -1285,8 +1286,7 @@ static int snd_korg1212_silence(struct snd_korg1212 *korg1212, int pos, int coun
>  }
>  
>  static int snd_korg1212_copy_to(struct snd_pcm_substream *substream,
> -				void __user *dst, int pos, int count,
> -				bool in_kernel)
> +				sockptr_t dst, int pos, int count)
>  {
>  	struct snd_pcm_runtime *runtime = substream->runtime;
>          struct snd_korg1212 *korg1212 = snd_pcm_substream_chip(substream);
> @@ -1306,24 +1306,21 @@ static int snd_korg1212_copy_to(struct snd_pcm_substream *substream,
>  #if K1212_DEBUG_LEVEL > 0
>  		if ( (void *) src < (void *) korg1212->recordDataBufsPtr ||
>  		     (void *) src > (void *) korg1212->recordDataBufsPtr[8].bufferData ) {
> -			printk(KERN_DEBUG "K1212_DEBUG: snd_korg1212_copy_to KERNEL EFAULT, src=%p dst=%p iter=%d\n", src, dst, i);
> +			printk(KERN_DEBUG "K1212_DEBUG: %s KERNEL EFAULT, src=%p dst=%p iter=%d\n",
> +			       __func__, src, sockptr_is_kernel(dst) ? dst.kernel : dst.user, i);
>  			return -EFAULT;
>  		}
>  #endif
> -		if (in_kernel)
> -			memcpy((__force void *)dst, src, size);
> -		else if (copy_to_user(dst, src, size))
> +		if (copy_to_sockptr_offset(dst, i * size, src, size))
>  			return -EFAULT;
>  		src++;
> -		dst += size;
>  	}
>  
>  	return 0;
>  }
>  
>  static int snd_korg1212_copy_from(struct snd_pcm_substream *substream,
> -				  void __user *src, int pos, int count,
> -				  bool in_kernel)
> +				  sockptr_t src, int pos, int count)
>  {
>          struct snd_pcm_runtime *runtime = substream->runtime;
>  	struct snd_korg1212 *korg1212 = snd_pcm_substream_chip(substream);
> @@ -1345,16 +1342,14 @@ static int snd_korg1212_copy_from(struct snd_pcm_substream *substream,
>  #if K1212_DEBUG_LEVEL > 0
>  		if ( (void *) dst < (void *) korg1212->playDataBufsPtr ||
>  		     (void *) dst > (void *) korg1212->playDataBufsPtr[8].bufferData ) {
> -			printk(KERN_DEBUG "K1212_DEBUG: snd_korg1212_copy_from KERNEL EFAULT, src=%p dst=%p iter=%d\n", src, dst, i);
> +			printk(KERN_DEBUG "K1212_DEBUG: %s KERNEL EFAULT, src=%p dst=%p iter=%d\n",
> +			       __func__, sockptr_is_kernel(src) ? src.kernel : src.user, dst, i);
>  			return -EFAULT;
>  		}
>  #endif
> -		if (in_kernel)
> -			memcpy(dst, (__force void *)src, size);
> -		else if (copy_from_user(dst, src, size))
> +		if (copy_from_sockptr_offset(dst, src, i * size, size))
>  			return -EFAULT;
>  		dst++;
> -		src += size;
>  	}
>  
>  	return 0;
> @@ -1644,15 +1639,14 @@ static int snd_korg1212_playback_copy(struct snd_pcm_substream *substream,
>  				      int channel, unsigned long pos,
>  				      void __user *src, unsigned long count)
>  {
> -	return snd_korg1212_copy_from(substream, src, pos, count, false);
> +	return snd_korg1212_copy_from(substream, USER_SOCKPTR(src), pos, count);
>  }
>  
>  static int snd_korg1212_playback_copy_kernel(struct snd_pcm_substream *substream,
>  				      int channel, unsigned long pos,
>  				      void *src, unsigned long count)
>  {
> -	return snd_korg1212_copy_from(substream, (void __user *)src,
> -				      pos, count, true);
> +	return snd_korg1212_copy_from(substream, KERNEL_SOCKPTR(src), pos, count);
>  }
>  
>  static int snd_korg1212_playback_silence(struct snd_pcm_substream *substream,
> @@ -1672,15 +1666,14 @@ static int snd_korg1212_capture_copy(struct snd_pcm_substream *substream,
>  				     int channel, unsigned long pos,
>  				     void __user *dst, unsigned long count)
>  {
> -	return snd_korg1212_copy_to(substream, dst, pos, count, false);
> +	return snd_korg1212_copy_to(substream, USER_SOCKPTR(dst), pos, count);
>  }
>  
>  static int snd_korg1212_capture_copy_kernel(struct snd_pcm_substream *substream,
>  				     int channel, unsigned long pos,
>  				     void *dst, unsigned long count)
>  {
> -	return snd_korg1212_copy_to(substream, (void __user *)dst,
> -				    pos, count, true);
> +	return snd_korg1212_copy_to(substream, KERNEL_SOCKPTR(dst), pos, count);
>  }
>  
>  static const struct snd_pcm_ops snd_korg1212_playback_ops = {
> -- 
> 2.40.0.1.gaa8946217a0b
>