Add spidev to the CFA-10049

Hi everyone,

This patchset probes spidev on the SSP3 bus where on the CFA-10049 there is a DAC.

It first adds the dt bindings for the spidev driver, and the proper node in the CFA-10049 device tree file.

Maxime

Maxime Ripard (2):
spi: spidev: Add device tree bindings
ARM: dts: cfa10049: Add spidev to drive the DAC on SSP3

 arch/arm/boot/dts/imx28-cfa10049.dts |    6 ++++++
 drivers/spi/spidev.c                 |   10 ++++++++++
 2 files changed, 16 insertions(+)

1.7.9.5

This will allow to probe spidev from device tree

---
 drivers/spi/spidev.c |   10 ++++++++++
 1 file changed, 10 insertions(+)

index 830adbe..8ae0660 100644
@@ -31,6 +31,8 @@
 #include <linux/mutex.h>
 #include <linux/slab.h>
 #include <linux/compat.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
 
 #include <linux/spi/spi.h>
 #include <linux/spi/spidev.h>

@@ -642,10 +644,18 @@ static int __devexit spidev_remove(struct spi_device *spi)
 	return 0;
 }
 
+static const struct of_device_id spidev_dt_ids[] = {
+	{ .compatible = "linux,spidev" },
+	{},
+};
+
+MODULE_DEVICE_TABLE(of, spidev_dt_ids);
+
 static struct spi_driver spidev_spi_driver = {
 	.driver = {
 		.name =		"spidev",
 		.owner =	THIS_MODULE,
+		.of_match_table = of_match_ptr(spidev_dt_ids),
 	},
 	.probe =	spidev_probe,
 	.remove =	__devexit_p(spidev_remove),

1.7.9.5

So, this isn't really something we should have in DT in this format -
the fact that we happen to control some device from userspace isn't a
generic property of the board really, we may end up changing our minds
on Linux too. The most obvious thing for this seems to be to add the
specific devices to spidev as the OF bindings rather than just register
as some non-specific "spidev" so we can change our minds later about how
to handle the devices. Not sure that's urgently tasteful but it does
mean we move the "we handle this in userspace" bit out of the .dts into
the kernel which seems better.
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Hi Mark,

Le 28/10/2012 00:19, Mark Brown a ?crit :

Ok, so I guess that leaves us with 2 choices here:
* Declare the device in the dt as you would have with any other driver, with its own compatible string, and we add this compatible string to the spidev dt ids array. It allows to use the existing code and thus doesn't require any effort at all, but it will generate a lot of noise for the spidev driver, since all of us will need to add its compatible string to spidev.
* Rework the spidev code so that it behaves mostly like i2c-dev, that is you have an instance of it for every device enumerated in the dt, regardless of wether it has a driver loaded or not. If the userspace opens the device file corresponding to a device already attached to a driver, you return EBUSY, and that's it. I guess it would be the cleaner solution, since you only select spidev in configuration, but it definitely requires way more development than the first one.

What's your views on this?
Did you have in mind another solution?

Thanks,
Maxime

Maxime Ripard, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com

I think either solution is good, obviously Grant's more the expert here.
Adding the IDs is obviously simpler and doesn't preclude later doing the
i2c-dev style thing so short term I'd probably add the IDs to get things
going and punt on the difficult stuff for the time being but YMMV.
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---
 arch/arm/boot/dts/imx28-cfa10049.dts |    6 ++++++
 1 file changed, 6 insertions(+)

index 05c892e..d91d16c 100644
@@ -29,6 +29,7 @@
 						0x01c1 /* MX28_PAD_GPMI_RESETN__SSP3_CMD */
 						0x0111 /* MX28_PAD_GPMI_CE1N__SSP3_D3 */
 						0x01a2 /* MX28_PAD_GPMI_ALE__SSP3_D4 */
+						0x01b2 /* MX28_PAD_GPMI_CLE__SSP3_D5 */
 					>;
 					fsl,drive-strength = <1>;
 					fsl,voltage = <1>;

@@ -60,6 +61,11 @@
 					spi-max-frequency = <100000>;
 				};
 
+				spidev: spidev at 2 {
+					compatible = "linux,spidev";
+					reg = <2>;
+					spi-max-frequency = <100000>;
+				};
 			};
 		};
 

1.7.9.5