Messages in this thread | | | Subject | Re: 答复: [PATCH] bus: mhi: core: Introd uce sysfs ul chan id for mhi chan device | From | Jeffrey Hugo <> | Date | Wed, 28 Oct 2020 08:17:32 -0600 |
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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@quectel.com wrote: >>>> From: "carl.yin" <carl.yin@quectel.com> >>>> >>>> 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@quectel.com> >>>> --- >>>> 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@quectel.com> >>>> +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.
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