Re: [PATCH ath-next v2 4/8] wifi: ath12k: add device DP stats reset support via debugfs

On 8/6/2026 6:24 AM, Pardeep Kaur wrote:
> From: Hariharan Ramanathan <[email protected]>
> 
> There is no way to reset device DP stats counters without reloading
> the driver, making it difficult to isolate issues to a specific time
> window during debugging.
> 
> Add a write handler to the device_dp_stats debugfs file so that
> writing 'reset' clears all device DP stats counters. Change the file
> mode from 0400 to 0600 to allow write access. Use strcmp() with
> newline stripping to match the input, consistent with the existing
> pattern in debugfs.c. Return -EINVAL on unrecognised input.
> 
> No lock is taken around the memset since the counters are updated
> locklessly in the datapath; taking dp_lock would be misleading as it
> does not protect device_stats updates.
> 
> Tested-on: QCN9274 hw2.0 PCI WLAN.WBE.1.6.r1-00402-QCAHKSWPL_SILICONZ-1
> 
> Signed-off-by: Hariharan Ramanathan <[email protected]>
> Co-developed-by: Pardeep Kaur <[email protected]>
> Signed-off-by: Pardeep Kaur <[email protected]>
> ---
>  drivers/net/wireless/ath/ath12k/debugfs.c | 35 ++++++++++++++++++++++-
>  1 file changed, 34 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/wireless/ath/ath12k/debugfs.c b/drivers/net/wireless/ath/ath12k/debugfs.c
> index ec49692107a8..0e446a666f4c 100644
> --- a/drivers/net/wireless/ath/ath12k/debugfs.c
> +++ b/drivers/net/wireless/ath/ath12k/debugfs.c
> @@ -1220,8 +1220,41 @@ static ssize_t ath12k_debugfs_dump_device_dp_stats(struct file *file,
>  	return ret;
>  }
>  
> +static ssize_t
> +ath12k_debugfs_write_device_dp_stats(struct file *file,
> +				     const char __user *user_buf,
> +				     size_t count, loff_t *ppos)
> +{
> +	struct ath12k_base *ab = file->private_data;
> +	struct ath12k_dp *dp = ath12k_ab_to_dp(ab);
> +	struct ath12k_device_dp_stats *device_stats = &dp->device_stats;
> +	char buf[20] = {};
> +	int ret;
> +
> +	if (count >= sizeof(buf))
> +		return -EINVAL;
> +
> +	ret = copy_from_user(buf, user_buf, count);
> +	if (ret)
> +		return -EFAULT;
> +
> +	/* drop the possible '\n' from the end */
> +	if (count > 0 && buf[count - 1] == '\n')
> +		buf[count - 1] = '\0';
> +

my review agent says:
The new ath12k_debugfs_write_device_dp_stats uses raw copy_from_user(buf,
user_buf, count) and never checks or advances *ppos. A write split across two
write(2) calls (non-zero ppos on the second) will copy the second chunk into
buf[0] instead of buf[ppos], silently failing to match "reset". The existing
ath12k_write_simulate_fw_crash in the same file (line 63) uses
simple_write_to_buffer(), which is the idiomatic kernel pattern here. Replace
with:
ret = simple_write_to_buffer(buf, sizeof(buf) - 1, ppos, user_buf, count);
if (ret <= 0)
    return ret;


> +	if (!strcmp(buf, "reset")) {
> +		memset(device_stats, 0, sizeof(*device_stats));
> +		return count;
> +	}
> +
> +	ath12k_warn(ab, "unsupported command: %s\n", buf);
> +
> +	return -EINVAL;
> +}
> +
>  static const struct file_operations fops_device_dp_stats = {
>  	.read = ath12k_debugfs_dump_device_dp_stats,
> +	.write = ath12k_debugfs_write_device_dp_stats,
>  	.open = simple_open,
>  	.owner = THIS_MODULE,
>  	.llseek = default_llseek,
> @@ -1232,7 +1265,7 @@ void ath12k_debugfs_pdev_create(struct ath12k_base *ab)
>  	debugfs_create_file("simulate_fw_crash", 0600, ab->debugfs_soc, ab,
>  			    &fops_simulate_fw_crash);
>  
> -	debugfs_create_file("device_dp_stats", 0400, ab->debugfs_soc, ab,
> +	debugfs_create_file("device_dp_stats", 0600, ab->debugfs_soc, ab,
>  			    &fops_device_dp_stats);
>  }
>