Re: [RFC 2/2] usb: gadget: composite: parse dt overrides

On 6/25/2012 1:49 PM, Rob Herring wrote:

On 06/25/2012 03:23 PM, Alexandre Pereira da Silva wrote:

quoted

Grab the devicetree node properties to override VendorId, ProductId,
bcdDevice, Manucacturer, Product and SerialNumber

Signed-off-by: Alexandre Pereira da Silva <redacted>
---
  drivers/usb/gadget/composite.c |   31 +++++++++++++++++++++++++++++++
  1 file changed, 31 insertions(+)

Are these bindings documented? I think they should be less generic.
Perhaps prefixed with 'usb-'.

There is precedent for the following properties in the USB node, namely 
the device tree that has been used on OLPC systems for the past several 
years.  Also, I think that Sun machines from the same timeframe use the 
same property names, based on the fact that Sun is using my USB 2.0 OFW 
driver code.

Here's a listing of the properties of a representative USB child device, 
in this case a USB FLASH drive.

configuration#           00000001
bulk-out-size            00000200
bulk-out-pipe            00000001
bulk-in-size             00000200
bulk-in-pipe             00000001
serial$                  200435137016ae938861
device$                  Cruzer Mini
vendor$                  SanDisk Corporation
compatible               usb781,5150.20
                          usb781,5150
                          usbif781,class8.6.50
                          usbif781,class8.6
                          usbif781,class8
                          usbif,class8.6.50
                          usbif,class8.6
                          usbif,class8
                          usb,device
vendor-id                00000781
device-id                00005150
release                  00000020
name                     scsi
class                    00000008
subclass                 00000006
protocol                 00000050
high-speed
assigned-address         00000002
reg                      00000003 00000000
#size-cells              00000000
#address-cells           00000001

Note that:

a) The separator in "vendor-id" is hyphen, not underscore, in keeping 
with the established property naming convention (except for the 
unfortunate "device_type").

b) There is no "usb," prefix, since the presence of this in a device 
node that is a child of a USB bus implicitly identifies the kind of ID. 
  "vendor-id" and "device-id" in PCI bus child devices is similarly 
un-prefixed.

c) Some of these property names are defined in 
http://www.openfirmware.org/ofwg/bindings/usb/usb-1_0.ps

quoted

diff --git a/drivers/usb/gadget/composite.c b/drivers/usb/gadget/composite.c
index 390749b..f3b480e 100644
--- a/drivers/usb/gadget/composite.c
+++ b/drivers/usb/gadget/composite.c

@@ -17,6 +17,7 @@
  #include <linux/module.h>
  #include <linux/device.h>
  #include <linux/utsname.h>
+#include <linux/of.h>

  #include <linux/usb/composite.h>
  #include <asm/unaligned.h>

@@ -1423,6 +1424,7 @@ static int composite_bind(struct usb_gadget *gadget)
  {
  	struct usb_composite_dev	*cdev;
  	int				status = -ENOMEM;
+	struct device_node		*np = gadget->dev.of_node;

  	cdev = kzalloc(sizeof *cdev, GFP_KERNEL);
  	if (!cdev)

@@ -1470,6 +1472,35 @@ static int composite_bind(struct usb_gadget *gadget)

  	cdev->desc = *composite->dev;

+	/* grab overrides from devicetree */

Reading the code, it looks more like the DT entries are defaults rather
than overrides.

quoted

+	if (np) {
+		u32 reg;
+
+		if (!idVendor &&
+			of_property_read_u32(np, "vendor_id", &reg) == 0)
+			idVendor = reg;

if (!idVendor)
	of_property_read_u32(np, "vendor_id", &idVendor);

Rob

quoted

+
+		if (!idProduct &&
+			of_property_read_u32(np, "product_id", &reg) == 0)
+			idProduct = reg;
+
+		if (!bcdDevice &&
+			of_property_read_u32(np, "bcd_device", &reg) == 0)
+			bcdDevice = reg;
+
+		if (!iManufacturer)
+			of_property_read_string(np, "manufacturer",
+				&iManufacturer);
+
+		if (!iProduct)
+			of_property_read_string(np, "product",
+				&iProduct);
+
+		if (!iSerialNumber)
+			of_property_read_string(np, "serial_number",
+				&iSerialNumber);
+	}
+
  	/* standardized runtime overrides for device ID data */
  	if (idVendor)
  		cdev->desc.idVendor = cpu_to_le16(idVendor);

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