linux-kernel - Re: [PATCH 03/25] ALSA: core: Add memory copy helpers between iov

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Date:   Tue, 15 Aug 2023 15:54:16 +0200
From:   Takashi Iwai <tiwai@...e.de>
To:     Andy Shevchenko <andriy.shevchenko@...el.com>
Cc:     alsa-devel@...a-project.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 03/25] ALSA: core: Add memory copy helpers between iov_iter and iomem

On Tue, 15 Aug 2023 15:51:30 +0200,
Andy Shevchenko wrote:
> 
> On Mon, Aug 14, 2023 at 01:55:01PM +0200, Takashi Iwai wrote:
> > Add two more helpers for copying memory between iov_iter and iomem,
> > which will be used by the new PCM copy ops in a few drivers.
> > The existing helpers became wrappers of those now.
> > 
> > Note that copy_from/to_iter() returns the copied bytes, hence the
> > error condition is inverted from copy_from/to_user().
> 
> ...
> 
> > -	return copy_to_user(dst, (const void __force*)src, count) ? -EFAULT : 0;
> > +	return !copy_to_iter((const void __force *)src, count, dst) ? -EFAULT : 0;
> 
> Inverted means, I believe, this
> 
> 	return copy_to_iter((const void __force *)src, count, dst) == count ? 0 : -EFAULT;
> 
> as far as I understand the idea behind the copy_to_user() return value.
> 
> Ditto for other cases.

OK, this looks more correct.  I'll fix in v2.


thanks,

Takashi