On Sun, Apr 26, 2015 at 04:14:33PM +0200, Michal Suchanek wrote: > On 26 April 2015 at 14:51, Maxime Ripard > <maxime.ripard@xxxxxxxxxxxxxxxxxx> wrote: > > 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. > > There is no device connected in the slot by design. The slot is there > for connecting random stuff you find in your mailbox or other drawers > and boxes. I know. Our point is add a compatible for that random device you find in your mailbox. > >> 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. > > There is nothing like unclaimed device. Either there is a device and > driver for it may in principle be loaded later as a module or the chip > select is reserved for use from userspace. I never said it was perfect. > Userspace driver is valid option and should have the ability to have > the chip select reserved. Whether an userspace driver is a valid option can spawn a whole debate by its own, but it's true that we should be able to have it exported to the userspace. However, having a spidev compatible is not the solution to that problem. > > 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? > > I have multitude of SPI devices which are not part of the board and > hence its DT and can be connected to the board with jumper wires. > > Most of them don't have a linux driver or compatible to bind with. Then create such a compatible... > >> 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. > > Yes, so I have this red rectangular PCB, blue PCB, and red square PCB > and blue very thin rectangular PCB. > > Please enlighten me how to add DT bindings for these and the PCB which > is in the mail and I did not pick up at the post office yet. > > Of course, I have some hope that the chips on the PCBs are at least > somewhat compatible with what I ordered but I cannot be sure until I > test that. Come on, this is pure bad faith. If you don't even know what that device is, how do you even know how to interact with it? Maxime -- Maxime Ripard, Free Electrons Embedded Linux, Kernel and Android engineering http://free-electrons.com
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