Thanks for your comments. Some nested below. > -----Original Message----- > From: Ville Syrjälä [mailto:ville.syrjala@xxxxxxxxxxxxxxx] > Sent: Wednesday, January 25, 2017 9:57 AM > To: Limonciello, Mario <Mario_Limonciello@xxxxxxxx> > Cc: intel-gfx@xxxxxxxxxxxxxxxxxxxxx > Subject: Re: DP Aux interfaces inquiry > > On Tue, Jan 24, 2017 at 07:51:28PM +0000, Mario.Limonciello@xxxxxxxx > wrote: > > Hi, > > > > Recently Synaptics collaborated with Dell on a plugin [1] for fwupd that > allows flashing Synaptics MST hubs using the DP aux interface to manipulate > the DPCD [2]. > > Currently the plugin hardcodes the max number of DP aux devices to look for > to 3 (as that's what we've seen so far on HW), but we were wondering: > > > > 1) If there is a way to query the number of devices that the kernel is > going to be creating? > > 2) Are there any instances of more than 3 devices in the wild today that > anyone is aware of? > > These depend on the board you're dealing with, and on the number of gpus you > have in the system (and whether they actually have drivers loaded for them). OK, that's what I was suspecting. > > We should also perhaps expose the aux device node for MST devices. At which > point the number of aux nodes could change dynamically when you plug MST > devices in/out. > Hmm, for the devices themselves? The way Synaptics handles cascaded MST devices today is a remote control mechanism. They're able to turn on remote control for one MST hub, and it will forward control commands (and payloads) to the next cascaded hub. If/when you do this can you send a uevent up to userspace? It would be good for fwupd to be able to listen to it and refresh devices based upon what happened from nodes coming and going. > So I don't think you should be making any assumptions on the number/order of > these device nodes. > >From userspace would it be better to just scan /dev for /dev/drm_dp_aux# nodes? No assumptions about the order of them, just look for all the ones with that prefix? If not, do you have a better recommendation on how to do this? _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
