On 10/27/2020 7:18 PM, Carl Yin(殷张成) wrote:
Hi Jeffery and Hemant:
On Wednesday, October 28, 2020 6:44 AM, hemantk wrote:
On 10/27/20 8:06 AM, Jeffrey Hugo wrote:
Hi Carl,
On 10/27/20 8:06 AM, Jeffrey Hugo wrote:
On 10/27/2020 3:43 AM, carl.yin@xxxxxxxxxxx wrote:
From: "carl.yin" <carl.yin@xxxxxxxxxxx>
User space software like ModemManager can identify the function of
the mhi chan device by ul_chan_id.
Signed-off-by: carl.yin <carl.yin@xxxxxxxxxxx>
---
Documentation/ABI/stable/sysfs-bus-mhi | 10 ++++++++++
drivers/bus/mhi/core/init.c | 15 +++++++++++++++
2 files changed, 25 insertions(+)
diff --git a/Documentation/ABI/stable/sysfs-bus-mhi
b/Documentation/ABI/stable/sysfs-bus-mhi
index ecfe766..6d52768 100644
--- a/Documentation/ABI/stable/sysfs-bus-mhi
+++ b/Documentation/ABI/stable/sysfs-bus-mhi
@@ -19,3 +19,13 @@ Description: The file holds the OEM PK Hash
value of the endpoint device
read without having the device power on at least once, the
file
will read all 0's.
Users: Any userspace application or clients interested in
device info.
+
+What: /sys/bus/mhi/devices/.../ul_chan_id
+Date: November 2020
+KernelVersion: 5.10
+Contact: Carl Yin <carl.yin@xxxxxxxxxxx>
+Description: The file holds the uplink chan id of the mhi chan
device.
+ User space software like ModemManager can identify the
function of
+ the mhi chan device. If the mhi device is not a chan device,
+ eg mhi controller device, the file read -1.
+Users: Any userspace application or clients interested in
device info.
diff --git a/drivers/bus/mhi/core/init.c
b/drivers/bus/mhi/core/init.c index c6b43e9..ac4aa5c 100644
--- a/drivers/bus/mhi/core/init.c
+++ b/drivers/bus/mhi/core/init.c
@@ -105,9 +105,24 @@ static ssize_t oem_pk_hash_show(struct device
*dev,
}
static DEVICE_ATTR_RO(oem_pk_hash);
+static ssize_t ul_chan_id_show(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ struct mhi_device *mhi_dev = to_mhi_device(dev);
+ int ul_chan_id = -1;
+
+ if (mhi_dev->ul_chan)
+ ul_chan_id = mhi_dev->ul_chan_id;
+
+ return snprintf(buf, PAGE_SIZE, "%d\n", ul_chan_id); } static
+DEVICE_ATTR_RO(ul_chan_id);
+
static struct attribute *mhi_dev_attrs[] = {
&dev_attr_serial_number.attr,
&dev_attr_oem_pk_hash.attr,
+ &dev_attr_ul_chan_id.attr,
NULL,
};
ATTRIBUTE_GROUPS(mhi_dev);
NACK
Channel ID is a device specific detail. Userspace should be basing
decisions on the channel name.
I agree with Jeff, why do you need to know the channel id, if you need to poll for
any device node to get created you can try to open the device node from user
space and wait until the device gets opened.
Are you trying to wait for EDL channels to get started using UCI ?
[carl.yin] In my opinion, mhi chan id is something like 'bInterfaceNumber' of USB device.
A USB device and several USB interfaces, and a mhi devices have 128 mhi chans.
Chan id is a physical attribute of one mhi chan.
Next is the udev info of one mhi chan:
# udevadm info -a /dev/mhi_0000\:03\:00.0_EDL
looking at parent device '/devices/pci0000:00/0000:00:1d.0/0000:03:00.0/0000:03:00.0_EDL':
KERNELS=="0000:03:00.0_EDL"
SUBSYSTEMS=="mhi"
DRIVERS=="mhi_uci"
ATTRS{serial_number}=="Serial Number: 2644481182"
ATTRS{ul_chan_id}=="34"
If no ul_chan_id, the udev ruler will be ' KERNEL=="*_EDL" '
I have several usecases where this works just fine today.
With ul_chan_id, the udev ruler will be ' ATTRS{ul_chan_id}=="34"'
This breaks when there is some new device that has the EDL channel on
some different chan_id, like 7. The above does not. Additionally if
there is a different device that is using chan_id 34 for a different
purpose, say Diag, then your udev rule also breaks.
The name of the channel is the interface to the channel. Not the
chan_id. This holds true within the kernel, and should be the same for
userspace. I still oppose this change.
--
Jeffrey Hugo
Qualcomm Technologies, Inc. is a member of the
Code Aurora Forum, a Linux Foundation Collaborative Project.
