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

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Message-ID: <ZNuC4qKYOR4piQQU@smile.fi.intel.com>
Date:   Tue, 15 Aug 2023 16:51:30 +0300
From:   Andy Shevchenko <andriy.shevchenko@...el.com>
To:     Takashi Iwai <tiwai@...e.de>
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 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.

-- 
With Best Regards,
Andy Shevchenko