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Wed, 28 Oct 2020 14:17:36 GMT Sender: jhugo=codeaurora.org@mg.codeaurora.org Received: by smtp.codeaurora.org (Postfix, from userid 1001) id E53A2C433CB; Wed, 28 Oct 2020 14:17:35 +0000 (UTC) Received: from [10.226.59.216] (i-global254.qualcomm.com [199.106.103.254]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) (Authenticated sender: jhugo) by smtp.codeaurora.org (Postfix) with ESMTPSA id 1F6B5C433C9; Wed, 28 Oct 2020 14:17:33 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 1F6B5C433C9 Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; spf=fail smtp.mailfrom=jhugo@codeaurora.org Subject: =?UTF-8?B?UmU6IOetlOWkjTogW1BBVENIXSBidXM6IG1oaTogY29yZTogSW50cm9k?= =?UTF-8?Q?uce_sysfs_ul_chan_id_for_mhi_chan_device?= To: =?UTF-8?B?Q2FybCBZaW4o5q635byg5oiQKQ==?= , Hemant Kumar , "manivannan.sadhasivam@linaro.org" , "sfr@canb.auug.org.au" Cc: "linux-arm-msm@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Naveen Kumar References: <1cdcb3c25ef3781b3baa2d6943cea3ea@sslemail.net> From: Jeffrey Hugo Message-ID: Date: Wed, 28 Oct 2020 08:17:32 -0600 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.3.2 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org 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" >>>> >>>> User space software like ModemManager can identify the function of >>>> the mhi chan device by ul_chan_id. >>>> >>>> Signed-off-by: carl.yin >>>> --- >>>>   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 >>>> +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.