On Sun, Apr 26, 2015 at 02:38:18PM +0200, Michal Suchanek wrote: > On 26 April 2015 at 13:56, Martin Sperl <kernel@xxxxxxxxxxxxxxxx> wrote: > > > >> On 26.04.2015, at 13:23, Hans de Goede <hdegoede@xxxxxxxxxx> wrote: > >> I think there is actual a use for just binding spidev as spidev, > >> think e.g. the spi pins on the raspberry pi. > >> > >> How do you deal we suggest with such a situation ? > > > > I actually asked the same question a few days ago on the spi list > > (in thread: "spi: spidev: Warn loudly if instantiated from DT as “spidev”) > > and the summary was: > > > > You can still do as before, but you have to accept that long > > irritating warning. > > > > Or you patch spidev.c to include your pattern of choice for compatiblity > > So the suggestion is to add a compatible string like olimex,uext-slot > to spidev and use that compatible in the DT? No, you add a compatible for the device that is connected to the bus through that slot. > That can certainly be done but adding a new compatible for every board > that has some random pins looks like a needless nuisance to me. > Especially compared to i2c where you can just open the bus so long as > ti is enabled. > > > > > Or you implement the following proposal (which needs a volunteer): > >> On 23.04.2015, at 09:42, Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote: > >> > >> So what you need is a way to handover from generic spidev to a device-specific > >> driver, cfr. what graphics drivers do when the device has been bound to by > >> vesafb or simplefb. > >> > >> Could this be implemented in a generic way in the spi or DT code? > > > > ... > >> On 23.04.2015, at 12:36, Mark Brown <broonie@xxxxxxxxxx> wrote: > >> On Thu, Apr 23, 2015 at 09:45:16AM +0200, Geert Uytterhoeven wrote: > >> > >>> I guess this has been suggested before: the spi core could provide spidev > >>> access to all spi client devices which are not bound by a driver? > >> > >> I don't know if it's been suggested before, certainly nobody did the > >> work to make it happen. I don't think I have a massive objection in > >> principal. Actually, I did it a year ago, and it looked at the time that it wasn't what should be done either. https://lkml.org/lkml/2014/4/28/612 > But how do you know there is a device? > > Devices on i2c can be probed. On spi you just transfer random data and > hope it does something useful. Some devices have readable registers > and can be probed in a device-specific way but others are write-only. Well, what's the point of communicating with a non-existent device in the first place? > So binding spidev is in my view just saying that you are going to > transfer random data from userspace on this bus. Yes, to a device connected on that bus. Maxime -- Maxime Ripard, Free Electrons Embedded Linux, Kernel and Android engineering http://free-electrons.com
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