[Intel-gfx] [PATCH 03/10] driver core: Flow the return code from ->probe() through to sysfs bind

Christoph Hellwig
2021-06-17T14:24:16Z

Currently really_probe() returns 1 on success and 0 if the probe() call
fails. This return code arrangement is designed to be useful for
__device_attach_driver() which is walking the device list and trying every
driver. 0 means to keep trying.

However, it is not useful for the other places that call through to
really_probe() that do actually want to see the probe() return code.

For instance bind_store() would be better to return the actual error code
from the driver's probe method, not discarding it and returning -ENODEV.

Reorganize things so that really_probe() returns the error code from
->probe as a (inverted) positive number, and 0 for successful attach.

With this, __device_attach_driver can ignore the (positive) probe errors,
return 1 to exit the loop for a successful binding and pass on the
other negative errors, while device_driver_attach simplify inverts the
positive errors and returns all errors to the sysfs code.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
---
drivers/base/bus.c | 6 +-----
drivers/base/dd.c | 29 ++++++++++++++++++++---------
2 files changed, 21 insertions(+), 14 deletions(-)

diff --git a/drivers/base/bus.c b/drivers/base/bus.c
index 7de13302e8c8..1f6b4bd61056 100644
--- a/drivers/base/bus.c
+++ b/drivers/base/bus.c
@@ -212,13 +212,9 @@ static ssize_t bind_store(struct device_driver *drv, const char *buf,
dev = bus_find_device_by_name(bus, NULL, buf);
if (dev && driver_match_device(drv, dev)) {
err = device_driver_attach(drv, dev);
-
- if (err > 0) {
+ if (!err) {
/* success */
err = count;
- } else if (err == 0) {
- /* driver didn't accept device */
- err = -ENODEV;
}
}
put_device(dev);
diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index fd83817240e6..25341f52198c 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -607,10 +607,10 @@ static int really_probe(struct device *dev, struct device_driver *drv)
probe_ret = call_driver_probe(dev, drv);
if (probe_ret) {
/*
- * Ignore errors returned by ->probe so that the next driver can
- * try its luck.
+ * Return probe errors as positive values so that the callers
+ * can distinguish them from other errors.
*/
- ret = 0;
+ ret = -probe_ret;
goto probe_failed;
}

@@ -653,7 +653,6 @@ static int really_probe(struct device *dev, struct device_driver *drv)
dev->pm_domain->sync(dev);

driver_bound(dev);
- ret = 1;
pr_debug("bus: '%s': %s: bound device %s to driver %s\n",
drv->bus->name, __func__, dev_name(dev), drv->name);
goto done;
@@ -746,8 +745,8 @@ EXPORT_SYMBOL_GPL(wait_for_device_probe);
* @dev: device to try to bind to the driver
*
* This function returns -ENODEV if the device is not registered, -EBUSY if it
- * already has a driver, and 1 if the device is bound successfully and 0
- * otherwise.
+ * already has a driver, 0 if the device is bound successfully and a positive
+ * (inverted) error code for failures from the ->probe method.
*
* This function must be called with @dev lock held. When called for a
* USB interface, @dev->parent lock must be held as well.
@@ -882,7 +881,14 @@ static int __device_attach_driver(struct device_driver *drv, void *_data)
if (data->check_async && async_allowed != data->want_async)
return 0;

- return driver_probe_device(drv, dev);
+ /*
+ * Ignore errors returned by ->probe so that the next driver can try
+ * its luck.
+ */
+ ret = driver_probe_device(drv, dev);
+ if (ret < 0)
+ return ret;
+ return ret == 0;
}

static void __device_attach_async_helper(void *_dev, async_cookie_t cookie)
@@ -1038,7 +1044,7 @@ static void __device_driver_unlock(struct device *dev, struct device *parent)
* @dev: Device to attach it to
*
* Manually attach driver to a device. Will acquire both @dev lock and
- * @dev->parent lock if needed.
+ * @dev->parent lock if needed. Returns 0 on success, -ERR on failure.
*/
int device_driver_attach(struct device_driver *drv, struct device *dev)
{
@@ -1048,6 +1054,9 @@ int device_driver_attach(struct device_driver *drv, struct device *dev)
ret = driver_probe_device(drv, dev);
__device_driver_unlock(dev, dev->parent);

+ /* also return probe errors as normal negative errnos */
+ if (ret > 0)
+ ret = -ret;
return ret;
}

@@ -1114,7 +1123,9 @@ static int __driver_attach(struct device *dev, void *data)
return 0;
}

- device_driver_attach(drv, dev);
+ __device_driver_lock(dev, dev->parent);
+ driver_probe_device(drv, dev);
+ __device_driver_unlock(dev, dev->parent);

return 0;
}
--
2.30.2