I'm looking at the code for binding platform devices with drivers.
However, platform_match() doesn't seem to agree with its kerneldoc
comment:
drivers/base/platform.c:
50 /**
51 * platform_match - bind platform device to platform driver.
52 * @dev: device.
53 * @drv: driver.
54 *
55 * Platform device IDs are assumed to be encoded like this:
56 * "<name><instance>", where <name> is a short description of the
57 * type of device, like "pci" or "floppy", and <instance> is the
58 * enumerated instance of the device, like '' or '42'.
59 * Driver IDs are simply "<name>".
60 * So, extract the <name> from the device, and compare it against
61 * the name of the driver. Return whether they match or not.
62 */
63
64 static int platform_match(struct device * dev, struct device_driver * drv)
65 {
66 struct platform_device *pdev = container_of(dev, struct platform_device, dev);
67
68 return (strncmp(pdev->name, drv->name, BUS_ID_SIZE) == 0);
69 }
Shouldn't that really be
64 static int platform_match(struct device * dev, struct device_driver * drv)
65 {
66 struct platform_device *pdev = container_of(dev, struct platform_device, dev);
67
68 return (strncmp(pdev->name, drv->name, strlen(drv->name)) == 0);
69 }
So that, for example, the 'floppy' driver will match with any of the
'floppy', 'floppy0' and 'floppy1' devices?
Later,
Kenn
On Sun, Apr 25, 2004 at 11:05:11PM +0100, Kenn Humborg wrote:
> I'm looking at the code for binding platform devices with drivers.
> However, platform_match() doesn't seem to agree with its kerneldoc
> comment:
The code is correct as stands. The documentation is behind times. All
platform devices are "<name><instance-number>" so it's correct that the
"floppy" driver matches "floppy0" and "floppy1" etc.
--
Russell King
Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/
maintainer of: 2.6 PCMCIA - http://pcmcia.arm.linux.org.uk/
2.6 Serial core
On Mon, Apr 26, 2004 at 12:00:50AM +0100, Russell King wrote:
> On Sun, Apr 25, 2004 at 11:05:11PM +0100, Kenn Humborg wrote:
> > I'm looking at the code for binding platform devices with drivers.
> > However, platform_match() doesn't seem to agree with its kerneldoc
> > comment:
>
> The code is correct as stands. The documentation is behind times. All
> platform devices are "<name><instance-number>" so it's correct that the
> "floppy" driver matches "floppy0" and "floppy1" etc.
Forgive me if I am being dense, but I still don't see how that works.
The current code:
return (strncmp(pdev->name, drv->name, BUS_ID_SIZE) == 0);
will only return 1 if pdev->name and drv->name are _identical_ for the
first 20 bytes. Which "floppy" and "floppy0" are not.
Could it be that all current platform devices are initially named
as "<name>" and the instance number is only appended after matching
has been done?
Later,
Kenn
On Mon, Apr 26, 2004 at 12:27:33AM +0100, Russell King wrote:
> pdev->name is the platform device name, which is just the <name> part.
> pdev->dev.bus_id is the device model name, which is <name><instance-number>,
> and the devices are known by this name.
>
> Rather than going to the trouble of parsing <name> from the device model
> name which would be inherently buggy, we reference it directly from the
> platform_device structure.
OK - I see it now.
> So, this comment needs updating:
>
> * So, extract the <name> from the device, and compare it against
> * the name of the driver. Return whether they match or not.
Want a patch?
Later,
Kenn
--- drivers/base/platform.c~ 2004-01-12 23:49:04.000000000 +0000
+++ drivers/base/platform.c 2004-04-26 00:33:43.000000000 +0100
@@ -57,8 +57,9 @@
* type of device, like "pci" or "floppy", and <instance> is the
* enumerated instance of the device, like '0' or '42'.
* Driver IDs are simply "<name>".
- * So, extract the <name> from the device, and compare it against
- * the name of the driver. Return whether they match or not.
+ * So, extract the <name> from the platform_device structure,
+ * and compare it against the name of the driver. Return whether
+ * they match or not.
*/
static int platform_match(struct device * dev, struct device_driver * drv)
On Mon, Apr 26, 2004 at 12:17:09AM +0100, Kenn Humborg wrote:
> On Mon, Apr 26, 2004 at 12:00:50AM +0100, Russell King wrote:
> > On Sun, Apr 25, 2004 at 11:05:11PM +0100, Kenn Humborg wrote:
> > > I'm looking at the code for binding platform devices with drivers.
> > > However, platform_match() doesn't seem to agree with its kerneldoc
> > > comment:
> >
> > The code is correct as stands. The documentation is behind times. All
> > platform devices are "<name><instance-number>" so it's correct that the
> > "floppy" driver matches "floppy0" and "floppy1" etc.
>
> Forgive me if I am being dense, but I still don't see how that works.
Sorry, I should've explained a little more.
pdev->name is the platform device name, which is just the <name> part.
pdev->dev.bus_id is the device model name, which is <name><instance-number>,
and the devices are known by this name.
Rather than going to the trouble of parsing <name> from the device model
name which would be inherently buggy, we reference it directly from the
platform_device structure.
So, this comment needs updating:
* So, extract the <name> from the device, and compare it against
* the name of the driver. Return whether they match or not.
--
Russell King
Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/
maintainer of: 2.6 PCMCIA - http://pcmcia.arm.linux.org.uk/
2.6 Serial core