From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kyle Roeschley Subject: Re: [PATCH] spi: Add a sysfs interface to instantiate devices Date: Fri, 22 Dec 2017 11:11:08 -0600 Message-ID: <20171222171108.GA31574@senary> References: <20171221200309.17967-1-kyle.roeschley@ni.com> <1513890342.26695.4.camel@impinj.com> <20171222155603.GM1827@finisterre> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Trent Piepho , "linux-spi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "geert-Td1EMuHUCqxL1ZNQvxDV9g@public.gmane.org" To: Mark Brown Return-path: Content-Disposition: inline In-Reply-To: <20171222155603.GM1827@finisterre> Sender: linux-spi-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: On Fri, Dec 22, 2017 at 03:56:03PM +0000, Mark Brown wrote: > On Thu, Dec 21, 2017 at 09:05:43PM +0000, Trent Piepho wrote: > > On Thu, 2017-12-21 at 14:03 -0600, Kyle Roeschley wrote: > > > Add a sysfs interface to instantiate and delete SPI devices using the > > > spidev driver. This can be used when developing a driver on a > > > self-soldered board which doesn't yet have proper SPI device declaration > > > at the platform level, and presumably for various debugging situations. > > > > Inspired by 99cd8e25875a ("i2c: Add a sysfs interface to instantiate > > > devices"). > > > The i2c interface allows one to specify the type of device to create. > > Why must this interface be linked to spidev and only capable of > > creating spidev devices? > > Right, that doesn't seem good. I also can't see anything in the actual > code which suggests that this is tied to spidev except the log messages. > Quoting Geert's email [1] on the subject: > To me, the above sounds a bit contradictive: either you have > 1. a simple (trivial) description, which can be handled by spidev and > userspace, and thus by just writing " spidev" to a new_device > sysfs node, or > 2. a complex description, for which you need a specialized in-kernel driver, > so you're gonna need a real DT node (and overlays?) to describe it. > > I don't think writing a complex description to a new_device sysfs node makes > sense. And regarding not being linked to spidev, see modalias in new_device_store: > > > + struct spi_board_info bi = { > > > + .modalias = "spidev", > > > + .max_speed_hz = ctlr->max_speed_hz, > > > + }; [1] https://marc.info/?l=linux-spi&m=151199390921251&w=2 Happy holidays, -- Kyle Roeschley Software Engineer National Instruments -- To unsubscribe from this list: send the line "unsubscribe linux-spi" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html