Re: [PATCH v3] platform/chrome: mfd/cros_ec_debugfs: Add debugfs entry to retrieve EC uptime.

[Enric Balletbo i Serra <enric.balletbo@collabora.com>]

On 8/4/19 13:29, Enric Balletbo i Serra wrote:
> Hi Tim,
> 
> Many thanks for sending this patch upstream, some comments below
> 
> On 27/3/19 19:20, Tim Wawrzynczak wrote:
>> The new debugfs entry 'uptime' is being made available to userspace so that
>> a userspace daemon can synchronize EC logs with host time.
>>
>> Signed-off-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
>> ---
>> Changelist:
>>  - Moved uptime file from sysfs to debugfs (/sys/kernel/debug/cros_ec/uptime)
>>  - Fixed ordering of local variables in cros_ec_uptime_read.
>> Tested against ChromeOS kernel v4.14
>> ---
>>  Documentation/ABI/testing/debugfs-cros-ec | 10 +++++
>>  drivers/platform/chrome/cros_ec_debugfs.c | 54 +++++++++++++++++++++++
>>  2 files changed, 64 insertions(+)
>>  create mode 100644 Documentation/ABI/testing/debugfs-cros-ec
>>
>> diff --git a/Documentation/ABI/testing/debugfs-cros-ec b/Documentation/ABI/testing/debugfs-cros-ec
>> new file mode 100644
>> index 000000000000..24b781c67a4c
>> --- /dev/null
>> +++ b/Documentation/ABI/testing/debugfs-cros-ec
> 
> Thanks to introduce the documentation!
> 
>> @@ -0,0 +1,10 @@
>> +What:		/sys/kernel/debug/cros_ec/uptime
> 
> Is that propriety only supported for the standard cros-ec?
> 
> If the answer is yes, is fine, but if this could be supported for other variants
> like cros_pd, cros_tp, cros_fp, cros_ish, etc. then I'd name it
> 
> /sys/kernel/debug/<ec-device-name>/uptime
> 
> 
>> +Date:		March 2019
>> +KernelVersion:	5.1
>> +Description:
>> +		Read-only.
>> +		Reads the EC's current uptime information
>> +		(using EC_CMD_GET_UPTIME_INFO) and prints
>> +		time_since_ec_boot_ms into the file.
>> +		This is used for synchronizing AP host time
>> +		with the cros_ec log.
>> diff --git a/drivers/platform/chrome/cros_ec_debugfs.c b/drivers/platform/chrome/cros_ec_debugfs.c
>> index 71308766e891..3ea42008a59e 100644
>> --- a/drivers/platform/chrome/cros_ec_debugfs.c
>> +++ b/drivers/platform/chrome/cros_ec_debugfs.c
>> @@ -201,6 +201,40 @@ static int cros_ec_console_log_release(struct inode *inode, struct file *file)
>>  	return 0;
>>  }
>>  
>> +static ssize_t cros_ec_uptime_read(struct file *file,
>> +				   char __user *user_buf,
>> +				   size_t count,
>> +				   loff_t *ppos)
>> +{
>> +	struct cros_ec_debugfs *debug_info = file->private_data;
>> +	struct cros_ec_device *ec_dev = debug_info->ec->ec_dev;
>> +	struct {
>> +		struct cros_ec_command msg;
>> +		struct ec_response_uptime_info resp;
>> +	} __packed ec_buf;
>> +	struct ec_response_uptime_info *resp;
>> +	struct cros_ec_command *msg;
>> +	char read_buf[32];
>> +	int ret;
>> +
>> +	msg = &ec_buf.msg;
>> +	resp = (struct ec_response_uptime_info *)msg->data;
>> +
>> +	msg->command = EC_CMD_GET_UPTIME_INFO;
>> +	msg->version = 0;
>> +	msg->insize = sizeof(*resp);
>> +	msg->outsize = 0;
>> +
>> +	ret = cros_ec_cmd_xfer_status(ec_dev, msg);
>> +	if (ret < 0)
>> +		return ret;
>> +
>> +	ret = scnprintf(read_buf, sizeof(read_buf), "%u\n",
>> +			resp->time_since_ec_boot_ms);
>> +
>> +	return simple_read_from_buffer(user_buf, count, ppos, read_buf, ret);
>> +}
>> +
>>  static ssize_t cros_ec_pdinfo_read(struct file *file,
>>  				   char __user *user_buf,
>>  				   size_t count,
>> @@ -269,6 +303,13 @@ const struct file_operations cros_ec_pdinfo_fops = {
>>  	.llseek = default_llseek,
>>  };
>>  
>> +const struct file_operations cros_ec_uptime_fops = {
>> +	.owner = THIS_MODULE,
>> +	.open = simple_open,
>> +	.read = cros_ec_uptime_read,
>> +	.llseek = default_llseek,
> 
> Should this file be seekable?
> 
>> +};
>> +
>>  static int ec_read_version_supported(struct cros_ec_dev *ec)
>>  {
>>  	struct ec_params_get_cmd_versions_v1 *params;
>> @@ -413,6 +454,15 @@ static int cros_ec_create_pdinfo(struct cros_ec_debugfs *debug_info)
>>  	return 0;
>>  }
>>  
>> +static int cros_ec_create_uptime(struct cros_ec_debugfs *debug_info)
>> +{
>> +	if (!debugfs_create_file("uptime", 0444, debug_info->dir, debug_info,
>> +				&cros_ec_uptime_fops))
>> +		return -ENOMEM;
> 
> When calling debugfs functions, there is no need to ever check the
> return value.  The function can work or not, but the code logic should
> never do something different based on this. This has been discussed recently on
> the LKML.
> 
> I know that this is currently wrong for the other entries in this file but let's
> try to do well and remove this function and just call debugfs_create_file in probe.
> 

Sorry, actually I changed my opinion on this. So you should check if the command
is supported and only expose that file if that is the case here. See this commit.

https://git.kernel.org/pub/scm/linux/kernel/git/chrome-platform/linux.git/commit/?h=for-next&id=ae8378b081fa970a65001de909d8d6d8deea79b7

> I plan to send patches to fix current status.
> 
>> +
>> +	return 0;
>> +}
>> +
>>  static int cros_ec_debugfs_probe(struct platform_device *pd)
>>  {
>>  	struct cros_ec_dev *ec = dev_get_drvdata(pd->dev.parent);
>> @@ -442,6 +492,10 @@ static int cros_ec_debugfs_probe(struct platform_device *pd)
>>  	if (ret)
>>  		goto remove_log;
>>  
>> +	ret = cros_ec_create_uptime(debug_info);
>> +	if (ret)
>> +		goto remove_log;
>> +
> 
>        debugfs_create_file("uptime", 0444, debug_info->dir, debug_info,
>                            &cros_ec_uptime_fops);
> 
>>  	ec->debug_info = debug_info;
>>  
>>  	dev_set_drvdata(&pd->dev, ec);
>>
> 
> Thanks,
>  Enric
>