linux-kernel - Re: [PATCH] OMAPDSS: restore "name" sysfs entry.

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Date:	Wed, 25 Feb 2015 11:32:18 +0200
From:	Tomi Valkeinen <tomi.valkeinen@...com>
To:	NeilBrown <neilb@...e.de>
CC:	"Dr. H. Nikolaus Schaller" <hns@...delico.com>,
	<linux-omap@...r.kernel.org>, <linux-fbdev@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>,
	GTA04 owners <gta04-owner@...delico.com>
Subject: Re: [PATCH] OMAPDSS: restore "name" sysfs entry.

On 25/02/15 11:20, NeilBrown wrote:

> Tested-by: NeilBrown <neilb@...e.de>
> 
> Before the patch:
> 
> # ls -l /sys/devices/platform/omapdss/display0 
> lrwxrwxrwx 1 root root 0 Feb  8 12:57 /sys/devices/platform/omapdss/display0 -> ../spi_lcd/spi_master/spi32766/spi32766.0
> 
> After the patch:
> 
> # ls -l /sys/devices/platform/omapdss/display0 
> total 0
> -r--r--r-- 1 root root 4096 Feb  8 13:37 display_name
> -rw-r--r-- 1 root root 4096 Feb  8 13:37 enabled
> -rw-r--r-- 1 root root 4096 Feb  8 13:37 mirror
> -r--r--r-- 1 root root 4096 Feb  8 13:37 name
> -rw-r--r-- 1 root root 4096 Feb  8 13:37 rotate
> -rw-r--r-- 1 root root 4096 Feb  8 13:37 tear_elim
> -rw-r--r-- 1 root root 4096 Feb  8 13:37 timings
> -rw-r--r-- 1 root root 4096 Feb  8 13:37 wss
> 
> 
> So as you say it creates a directory just for the display0 device, and that
> has the 'name' that we want.

I think this was something similar than how the sysfs files were set up
originally for omapdss. If I remember right, we didn't have proper
devices for the displays then. Things have evolved quite a bit since then.

There's a small chance of this patch breaking things, of course... If
someone accessed those display sysfs files via the display device
(../spi_lcd/spi_master/spi32766/spi32766.0), the files are now gone.

But I think (hope...) they are always accessed via the omapdss's
displayX directories.

> This works for me, and it seems to me to be a better fit to the general
> structure of /sys/devices - symlinks within /sys/devices are a substantial
> minority, other than 'subsystem', 'device', 'driver' and 'bdi' which have
> very generic meanings.
> 
> I guess I'm a little surprised that there doesn't seem to be any linkage from
> the display0 to the spi device.  Maybe that isn't important.

Yep, I don't think so. In any case, all this is to be deprecated, and as
soon as omapdrm driver works reliably that should be the driver to use.

So of course we need to keep omapfb working for the years to come, but
I'd rather not add any new sysfs files for a soon deprecated driver.

 Tomi

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