From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Alexander E. Patrakov" Date: Thu, 13 Feb 2014 06:37:51 +0000 Subject: Re: Fixing the kernels backlight API Message-Id: <52FC683F.10905@gmail.com> List-Id: References: <52FB8F45.9060006@redhat.com> <20140212204311.GH3891@intel.com> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: David Herrmann , =?ISO-8859-1?Q?Ville_Syrj=E4?= =?ISO-8859-1?Q?l=E4?= Cc: Linux Fbdev development list , Jingoo Han , "xorg-devel-go0+a7rfsptAfugRpC6u6w@public.gmane.org" , dri-devel , Hans de Goede , Dave Airlie 13.02.2014 04:26, David Herrmann wrote: > The "attach" stuff actually sounds doable, but who decides which one > to attach? You still need some user-space script during device-plug > for that. > But to be honest, the simplest way would be a "backlightd" > bus-activatable daemon. SetBacklight() then takes a DRM-connector and > brightness-value, which the daemon looks up in /sys and sets.. This > has the advantage that we can do any fancy matching in user-space. We > can provide quirks (maybe even via udev-hwdb) and other helpers for > weird setups. What would be done with Samsung monitors (like an old SyncMaster 770P) that have a DVI connection, no physical buttons and have to be controlled via DDC-CI? Currently, ddccontrol works (via /dev/i2c-*), but only from root. I would like this use case to be covered in such a way that it could work both in Xorg and in Wayland, and, if possible, without races related to i2c usage from the kernel and from userspace. -- Alexander E. Patrakov