Re: [PATCH v1 1/1] mux: Add new API to get mux_control ref by device name.

From: Kuppuswamy, Sathyanarayanan
Date: Sat Jul 08 2017 - 19:24:55 EST

Hi Peter,

On 7/8/2017 2:12 PM, Peter Rosin wrote:
On 2017-07-08 00:03, sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx wrote:
From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>

Currently this driver only provides a single API, mux_control_get() to
get mux_control reference based on mux_name, and also this API has tight
dependency on device tree node. For devices, that does not use device
tree, it makes it difficult to use this API. This patch adds new
API to access mux_control reference based on device name, chip index and
controller index value.
I assume this is for the Intel USB Multiplexer that you sent a driver for
a month or so ago? If so, you still have not answered these questions:
I am not planning to merge the Intel USB MUX driver any more. I agree with Hans comments
and decided not to proceed further on this approach.

But I created these helper functions to get my driver working with MUX framework. Since these
helper functions can be useful for any non-dt drivers who wants to use MUX framework, I thought
to submit these changes for review.

Is any other consumer in the charts at all? Can this existing consumer
ever make use of some other mux? If the answer to both those questions
are 'no', then I do not see much point in involving the mux subsystem at
all. The Broxton USB PHY driver could just as well write to the register
all by itself, no?

that I asked in https://lkml.org/lkml/2017/5/31/58

What is the point of that driver?

Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
---
drivers/mux/mux-core.c | 114 +++++++++++++++++++++++++++++++++++++++++++
include/linux/mux/consumer.h | 6 ++-
2 files changed, 119 insertions(+), 1 deletion(-)

diff --git a/drivers/mux/mux-core.c b/drivers/mux/mux-core.c
index 90b8995..f8796b9 100644
--- a/drivers/mux/mux-core.c
+++ b/drivers/mux/mux-core.c
@@ -422,6 +422,87 @@ static struct mux_chip *of_find_mux_chip_by_node(struct device_node *np)
return dev ? to_mux_chip(dev) : NULL;
}
+static int dev_parent_name_match(struct device *dev, const void *data)
+{
+ const char *devname = dev_name(dev->parent);
+ unsigned int i;
+
+ if (!devname || !data)
+ return 0;
+
+ for (i = 0; i < strlen(devname); i++) {
+ if (devname[i] == '.')
+ break;
+ }
+
+ return !strncmp(devname, data, i-1);
Ouch, strlen as a termination test is wasteful, you want to remove the loop
and do something like this

return !strncmp(devname, data, strcspn(devname, "."));
will fix it in next version.

+}
+
+/**
+ * mux_chip_get_by_index() - Get the mux-chip associated with give device.
+ * @devname: Name of the device which registered the mux-chip.
+ * @index: Index of the mux chip.
+ *
+ * Return: A pointer to the mux-chip, or an ERR_PTR with a negative errno.
+ */
+static struct mux_chip *mux_chip_get_by_index(const char *devname, int index)
+{
+ struct device *dev;
+ int found = -1;
+
+ if (!devname)
+ return ERR_PTR(-EINVAL);
+
+ do {
+ dev = class_find_device(&mux_class, NULL, devname,
+ dev_parent_name_match);
+
+ if (dev != NULL)
+ found++;
+
+ if (found >= index)
+ break;
+ } while (dev != NULL);
This loop is broken. class_find_device will always return the same device.
Good catch. I did not test the case with multiple chips. So I failed to notice this.

Also, if you fix the loop, why is the ordering stable and something to rely
on?

+
+ if ((found == index) && dev)
+ return to_mux_chip(dev);
+
+ return ERR_PTR(-ENODEV);
+}
+
+/**
+ * mux_control_get_by_index() - Get the mux-control of given device based on
+ * device name, chip and control index.
+ * @devname: Name of the device which registered the mux-chip.
+ * @chip_index: Index of the mux chip.
+ * @ctrl_index: Index of the mux controller.
+ *
+ * Return: A pointer to the mux-control, or an ERR_PTR with a negative errno.
+ */
+struct mux_control *mux_control_get_by_index(const char *devname,
+ unsigned int chip_index,
+ unsigned int ctrl_index)
+{
+ struct mux_chip *mux_chip;
+
+ mux_chip = mux_chip_get_by_index(devname, chip_index);
+
+ if (IS_ERR(mux_chip))
+ return ERR_PTR(PTR_ERR(mux_chip));
+
+ if (ctrl_index >= mux_chip->controllers) {
+ dev_err(&mux_chip->dev,
+ "Invalid controller index, maximum value is %d\n",
+ mux_chip->controllers);
+ return ERR_PTR(-EINVAL);
+ }
+
+ get_device(&mux_chip->dev);
+
+ return &mux_chip->mux[ctrl_index];
+}
+EXPORT_SYMBOL_GPL(mux_control_get_by_index);
+
/**
* mux_control_get() - Get the mux-control for a device.
* @dev: The device that needs a mux-control.
@@ -533,6 +614,39 @@ struct mux_control *devm_mux_control_get(struct device *dev,
}
EXPORT_SYMBOL_GPL(devm_mux_control_get);
+/**
+ * devm_mux_control_get_by_index() - Get the mux-control for a device of given
+ * index value.
+ * @dev: The device that needs a mux-control.
+ * @devname: Name of the device which registered the mux-chip.
+ * @chip_index: Index of the mux chip.
+ * @ctrl_index: Index of the mux controller.
+ *
+ * Return: Pointer to the mux-control, or an ERR_PTR with a negative errno.
+ */
+struct mux_control *devm_mux_control_get_by_index(struct device *dev,
+ const char *devname, unsigned int chip_index,
+ unsigned int ctrl_index)
+{
+ struct mux_control **ptr, *mux;
+
+ ptr = devres_alloc(devm_mux_control_release, sizeof(*ptr), GFP_KERNEL);
+ if (!ptr)
+ return ERR_PTR(-ENOMEM);
+
+ mux = mux_control_get_by_index(devname, chip_index, ctrl_index);
+ if (IS_ERR(mux)) {
+ devres_free(ptr);
+ return mux;
+ }
+
+ *ptr = mux;
+ devres_add(dev, ptr);
+
+ return mux;
+}
+EXPORT_SYMBOL_GPL(devm_mux_control_get_by_index);
+
/*
* Using subsys_initcall instead of module_init here to try to ensure - for
* the non-modular case - that the subsystem is initialized when mux consumers
diff --git a/include/linux/mux/consumer.h b/include/linux/mux/consumer.h
index 5577e1b..e02485b 100644
--- a/include/linux/mux/consumer.h
+++ b/include/linux/mux/consumer.h
@@ -28,5 +28,9 @@ void mux_control_put(struct mux_control *mux);
struct mux_control *devm_mux_control_get(struct device *dev,
const char *mux_name);
-
+struct mux_control *mux_control_get_by_index(const char *devname,
+ unsigned int chip_index, unsigned int ctrl_index);
+struct mux_control *devm_mux_control_get_by_index(struct device *dev,
+ const char *devname, unsigned int chip_index,
+ unsigned int ctrl_index);
I want an empty line here.
Got it.

Cheers,
peda

#endif /* _LINUX_MUX_CONSUMER_H */