Re: [PATCH 09/28] drm/dp_mst: Refactor build_mst_prop_path() to use seq_buf

[lyude]

Reviewed-by: Lyude Paul <lyude@xxxxxxxxxx>

Also, out of curiosity - how exactly are you able to get this many
email addresses in To: without your emails getting rejected? Because it
is literally impossible to respond to this email with all of them, and
this has been consistently kind of an issue when trying to submit patch
series that do large refactors like this.

On Tue, 2026-09-15 at 08:18 +0000, Bill Wendling wrote:
> build_mst_prop_path() constructs an MST property path by formatting
> port
> numbers into a temporary buffer and appending them to "proppath" with
> strlcat() in a loop.
> 
> In preparation for removing the deprecated strlcat() API[1], use
> struct
> seq_buf and seq_buf_printf() to format the path components directly
> into
> "proppath", eliminating the temporary buffer and repeated string
> scans.
> 
> Link: https://github.com/KSPP/linux/issues/370 [1]
> Cc: codemender-patching+linux@xxxxxxxxxx
> Assisted-by: Claude-3-5-Sonnet:20241022 [editor_update_file,
> make_kernel_build_single_file]
> Signed-off-by: Bill Wendling <morbo@xxxxxxxxxx>
> ---
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> ---
>  drivers/gpu/drm/display/drm_dp_mst_topology.c | 15 +++++++++------
>  1 file changed, 9 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/display/drm_dp_mst_topology.c
> b/drivers/gpu/drm/display/drm_dp_mst_topology.c
> index 7ce9e212770a..229b5fec44bf 100644
> --- a/drivers/gpu/drm/display/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c
> @@ -29,6 +29,7 @@
>  #include <linux/kernel.h>
>  #include <linux/random.h>
>  #include <linux/sched.h>
> +#include <linux/seq_buf.h>
>  #include <linux/seq_file.h>
>  
>  #if IS_ENABLED(CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS)
> @@ -2216,19 +2217,21 @@ static void build_mst_prop_path(const struct
> drm_dp_mst_branch *mstb,
>  				char *proppath,
>  				size_t proppath_size)
>  {
> +	struct seq_buf s;
>  	int i;
> -	char temp[8];
>  
> -	snprintf(proppath, proppath_size, "mst:%d", mstb->mgr-
> >conn_base_id);
> +	seq_buf_init(&s, proppath, proppath_size);
> +
> +	seq_buf_printf(&s, "mst:%d", mstb->mgr->conn_base_id);
>  	for (i = 0; i < (mstb->lct - 1); i++) {
>  		int shift = (i % 2) ? 0 : 4;
>  		int port_num = (mstb->rad[i / 2] >> shift) & 0xf;
>  
> -		snprintf(temp, sizeof(temp), "-%d", port_num);
> -		strlcat(proppath, temp, proppath_size);
> +		seq_buf_printf(&s, "-%d", port_num);
>  	}
> -	snprintf(temp, sizeof(temp), "-%d", pnum);
> -	strlcat(proppath, temp, proppath_size);
> +	seq_buf_printf(&s, "-%d", pnum);
> +
> +	seq_buf_str(&s);
>  }
>  
>  /**