linux-kernel - Re: [PATCH] sysfs: make sysfs_emit() return ssize

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Date: Thu, 7 Mar 2024 22:04:41 +0000
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: Alexey Dobriyan <adobriyan@...il.com>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sysfs: make sysfs_emit() return ssize_t

On Mon, Feb 05, 2024 at 01:11:36PM +0300, Alexey Dobriyan wrote:
> sysfs_emit() is most often found in functions returning ssize_t
> not int:
> 
> 	static ssize_t oops_count_show(...)
> 	{
> 		return sysfs_emit(page, ...);
> 	}
> 
> This pattern results in sign-extension instruction between
> sysfs_emit() return value (int) and caller return value (which is
> ssize_t).

Is that a problem?

> But it is better to do sign-extension once inside sysfs_emit()
> then duplicate it at nearly every call site on 64-bit.

Why is that better?  Does this affect code generation?  If so, how much?
And to what affect?

And the function itself really is dealing with an int, it's up to the
caller to want to do something with that, not the sysfs_emit() call
itself.

thanks,

greg k-h