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Update comments for DEVICE_PROBE() to reflect that BUS_PROBE_DEFAULT is

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now the preferred typical return value from a probe routine.  Discourage
the use of 0 (BUS_PROBE_SPECIFIC) as it should be used very rarely.
Point the reader to the DEVICE_PROBE(9) manpage for more detailed notes
on possible probe return values.

Submitted by:	Philip Soeberg  philip-dev of soeberg net
This commit is contained in:
John Baldwin 2011-05-24 13:22:40 +00:00
parent 211d4a2c42
commit af21235ac4
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=222253
1 changed files with 11 additions and 9 deletions
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20
sys/kern/device_if.m
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@ -89,28 +89,29 @@ CODE {
* the probe before returning. The return value of DEVICE_PROBE()
* is used to elect which driver is used - the driver which returns
* the largest non-error value wins the election and attaches to
* the device.
* the device. Common non-error values are described in the
* DEVICE_PROBE(9) manual page.
*
* If a driver matches the hardware, it should set the device
* description string using device_set_desc() or
* device_set_desc_copy(). This string is
* used to generate an informative message when DEVICE_ATTACH()
* is called.
* device_set_desc_copy(). This string is used to generate an
* informative message when DEVICE_ATTACH() is called.
*
* As a special case, if a driver returns zero, the driver election
* is cut short and that driver will attach to the device
* immediately.
* immediately. This should rarely be used.
*
* For example, a probe method for a pci device driver might look
* For example, a probe method for a PCI device driver might look
* like this:
*
* @code
* int foo_probe(device_t dev)
* int
* foo_probe(device_t dev)
* {
* if (pci_get_vendor(dev) == FOOVENDOR &&
* pci_get_device(dev) == FOODEVICE) {
* device_set_desc(dev, "Foo device");
* return (0);
* return (BUS_PROBE_DEFAULT);
* }
* return (ENXIO);
* }
@ -125,7 +126,8 @@ CODE {
*
* @param dev the device to probe
*
* @retval 0 if the driver strongly matches this device
* @retval 0 if this is the only possible driver for this
* device
* @retval negative if the driver can match this device - the
* least negative value is used to select the
* driver