linux-kernel - Re: [PATCH 1/3] platform/chrome: cros_ec_debugfs: Add debugfs entry to retrieve EC uptime

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Date:   Tue, 18 Jun 2019 10:45:01 +0200
From:   Enric Balletbo i Serra <enric.balletbo@...labora.com>
To:     linux-kernel@...r.kernel.org
Cc:     Collabora Kernel ML <kernel@...labora.com>, groeck@...omium.org,
        bleung@...omium.org, dtor@...omium.org,
        Tim Wawrzynczak <twawrzynczak@...omium.org>
Subject: Re: [PATCH 1/3] platform/chrome: cros_ec_debugfs: Add debugfs entry
 to retrieve EC uptime

Hi Tim,

On 14/6/19 13:15, Enric Balletbo i Serra wrote:
> From: Tim Wawrzynczak <twawrzynczak@...omium.org>
> 
> 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@...omium.org>
> [rework based on Tim's first approach]
> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@...labora.com>

Applied this patch and the others in the series for chrome-platform-5.3

Thanks,
~ Enric

> ---
> Hi Tim,
> 
> Sorry for beating around the bush a bit. I did a small rework of the
> latest patch you sent and now is more close to the first versions you
> sent. I was spinning around the idea if we should expose the attribute
> when the command is supported or not and I ended with the conclusion,
> however, I think makes sense for sysfs attributes, but I'd prefer
> simplicity in the code for debugfs, at the end, if we try to read a file
> for a non supported command we will get an error which is also useful
> debug information.
> 
> Could you recheck that the patch still works and that I didn't break
> anything, please?
> 
> Cheers,
> ~ Enric
> 
>  Documentation/ABI/testing/debugfs-cros-ec |  8 +++++
>  drivers/platform/chrome/cros_ec_debugfs.c | 38 +++++++++++++++++++++++
>  2 files changed, 46 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..c91da2d374aa
> --- /dev/null
> +++ b/Documentation/ABI/testing/debugfs-cros-ec
> @@ -0,0 +1,8 @@
> +What:		/sys/kernel/debug/<cros-ec-device>/uptime
> +Date:		June 2019
> +KernelVersion:	5.3
> +Description:
> +		A u32 providing the time since EC booted in ms. This is
> +		is used for synchronizing the AP host time with the EC
> +		log. An error is returned if the command is not supported
> +		by the EC or there is a communication problem.
> diff --git a/drivers/platform/chrome/cros_ec_debugfs.c b/drivers/platform/chrome/cros_ec_debugfs.c
> index 4578eb3e0731..970ba13df9a1 100644
> --- a/drivers/platform/chrome/cros_ec_debugfs.c
> +++ b/drivers/platform/chrome/cros_ec_debugfs.c
> @@ -241,6 +241,34 @@ static ssize_t cros_ec_pdinfo_read(struct file *file,
>  				       read_buf, p - read_buf);
>  }
>  
> +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 cmd;
> +		struct ec_response_uptime_info resp;
> +	} __packed msg = {};
> +	struct ec_response_uptime_info *resp;
> +	char read_buf[32];
> +	int ret;
> +
> +	resp = (struct ec_response_uptime_info *)&msg.resp;
> +
> +	msg.cmd.command = EC_CMD_GET_UPTIME_INFO;
> +	msg.cmd.insize = sizeof(*resp);
> +
> +	ret = cros_ec_cmd_xfer_status(ec_dev, &msg.cmd);
> +	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 const struct file_operations cros_ec_console_log_fops = {
>  	.owner = THIS_MODULE,
>  	.open = cros_ec_console_log_open,
> @@ -257,6 +285,13 @@ static 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,
> +};
> +
>  static int ec_read_version_supported(struct cros_ec_dev *ec)
>  {
>  	struct ec_params_get_cmd_versions_v1 *params;
> @@ -408,6 +443,9 @@ static int cros_ec_debugfs_probe(struct platform_device *pd)
>  	debugfs_create_file("pdinfo", 0444, debug_info->dir, debug_info,
>  			    &cros_ec_pdinfo_fops);
>  
> +	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);
>