drm/msm/dp: Simplify the dp_debug debugfs show function

The "dp_debug" show function allocates a buffer and piecemeal appends
line by line, checking for buffer overflows etc.

Migrate the function to seq_file, to remove all the extra book keeping
and simplify the function.

Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20211007190211.3158868-1-bjorn.andersson@linaro.org
Signed-off-by: Rob Clark <robdclark@chromium.org>

1 files changed, 25 insertions, 138 deletions

diff --git a/drivers/gpu/drm/msm/dp/dp_debug.c b/drivers/gpu/drm/msm/dp/dp_debug.c
index 4963d21fcdd9..da4323556ef3 100644
--- a/drivers/gpu/drm/msm/dp/dp_debug.c
+++ b/drivers/gpu/drm/msm/dp/dp_debug.c
@@ -31,177 +31,69 @@ struct dp_debug_private {
 	struct dp_debug dp_debug;
 };
 
-static int dp_debug_check_buffer_overflow(int rc, int *max_size, int *len)
+static int dp_debug_show(struct seq_file *seq, void *p)
 {
-	if (rc >= *max_size) {
-		DRM_ERROR("buffer overflow\n");
-		return -EINVAL;
-	}
-	*len += rc;
-	*max_size = SZ_4K - *len;
-
-	return 0;
-}
-
-static ssize_t dp_debug_read_info(struct file *file, char __user *user_buff,
-		size_t count, loff_t *ppos)
-{
-	struct dp_debug_private *debug = file->private_data;
-	char *buf;
-	u32 len = 0, rc = 0;
+	struct dp_debug_private *debug = seq->private;
 	u64 lclk = 0;
-	u32 max_size = SZ_4K;
 	u32 link_params_rate;
-	struct drm_display_mode *drm_mode;
+	const struct drm_display_mode *drm_mode;
 
 	if (!debug)
 		return -ENODEV;
 
-	if (*ppos)
-		return 0;
-
-	buf = kzalloc(SZ_4K, GFP_KERNEL);
-	if (!buf)
-		return -ENOMEM;
-
 	drm_mode = &debug->panel->dp_mode.drm_mode;
 
-	rc = snprintf(buf + len, max_size, "\tname = %s\n", DEBUG_NAME);
-	if (dp_debug_check_buffer_overflow(rc, &max_size, &len))
-		goto error;
-
-	rc = snprintf(buf + len, max_size,
-			"\tdp_panel\n\t\tmax_pclk_khz = %d\n",
+	seq_printf(seq, "\tname = %s\n", DEBUG_NAME);
+	seq_printf(seq, "\tdp_panel\n\t\tmax_pclk_khz = %d\n",
 			debug->panel->max_pclk_khz);
-	if (dp_debug_check_buffer_overflow(rc, &max_size, &len))
-		goto error;
-
-	rc = snprintf(buf + len, max_size,
-			"\tdrm_dp_link\n\t\trate = %u\n",
+	seq_printf(seq, "\tdrm_dp_link\n\t\trate = %u\n",
 			debug->panel->link_info.rate);
-	if (dp_debug_check_buffer_overflow(rc, &max_size, &len))
-		goto error;
-
-	rc = snprintf(buf + len, max_size,
-			 "\t\tnum_lanes = %u\n",
+	seq_printf(seq, "\t\tnum_lanes = %u\n",
 			debug->panel->link_info.num_lanes);
-	if (dp_debug_check_buffer_overflow(rc, &max_size, &len))
-		goto error;
-
-	rc = snprintf(buf + len, max_size,
-			"\t\tcapabilities = %lu\n",
+	seq_printf(seq, "\t\tcapabilities = %lu\n",
 			debug->panel->link_info.capabilities);
-	if (dp_debug_check_buffer_overflow(rc, &max_size, &len))
-		goto error;
-
-	rc = snprintf(buf + len, max_size,
-			"\tdp_panel_info:\n\t\tactive = %dx%d\n",
+	seq_printf(seq, "\tdp_panel_info:\n\t\tactive = %dx%d\n",
 			drm_mode->hdisplay,
 			drm_mode->vdisplay);
-	if (dp_debug_check_buffer_overflow(rc, &max_size, &len))
-		goto error;
-
-	rc = snprintf(buf + len, max_size,
-			"\t\tback_porch = %dx%d\n",
+	seq_printf(seq, "\t\tback_porch = %dx%d\n",
 			drm_mode->htotal - drm_mode->hsync_end,
 			drm_mode->vtotal - drm_mode->vsync_end);
-	if (dp_debug_check_buffer_overflow(rc, &max_size, &len))
-		goto error;
-
-	rc = snprintf(buf + len, max_size,
-			"\t\tfront_porch = %dx%d\n",
+	seq_printf(seq, "\t\tfront_porch = %dx%d\n",
 			drm_mode->hsync_start - drm_mode->hdisplay,
 			drm_mode->vsync_start - drm_mode->vdisplay);
-	if (dp_debug_check_buffer_overflow(rc, &max_size, &len))
-		goto error;
-
-	rc = snprintf(buf + len, max_size,
-			"\t\tsync_width = %dx%d\n",
+	seq_printf(seq, "\t\tsync_width = %dx%d\n",
 			drm_mode->hsync_end - drm_mode->hsync_start,
 			drm_mode->vsync_end - drm_mode->vsync_start);
-	if (dp_debug_check_buffer_overflow(rc, &max_size, &len))
-		goto error;
-
-	rc = snprintf(buf + len, max_size,
-			"\t\tactive_low = %dx%d\n",
+	seq_printf(seq, "\t\tactive_low = %dx%d\n",
 			debug->panel->dp_mode.h_active_low,
 			debug->panel->dp_mode.v_active_low);
-	if (dp_debug_check_buffer_overflow(rc, &max_size, &len))
-		goto error;
-
-	rc = snprintf(buf + len, max_size,
-			"\t\th_skew = %d\n",
+	seq_printf(seq, "\t\th_skew = %d\n",
 			drm_mode->hskew);
-	if (dp_debug_check_buffer_overflow(rc, &max_size, &len))
-		goto error;
-
-	rc = snprintf(buf + len, max_size,
-			"\t\trefresh rate = %d\n",
+	seq_printf(seq, "\t\trefresh rate = %d\n",
 			drm_mode_vrefresh(drm_mode));
-	if (dp_debug_check_buffer_overflow(rc, &max_size, &len))
-		goto error;
-
-	rc = snprintf(buf + len, max_size,
-			"\t\tpixel clock khz = %d\n",
+	seq_printf(seq, "\t\tpixel clock khz = %d\n",
 			drm_mode->clock);
-	if (dp_debug_check_buffer_overflow(rc, &max_size, &len))
-		goto error;
-
-	rc = snprintf(buf + len, max_size,
-			"\t\tbpp = %d\n",
+	seq_printf(seq, "\t\tbpp = %d\n",
 			debug->panel->dp_mode.bpp);
-	if (dp_debug_check_buffer_overflow(rc, &max_size, &len))
-		goto error;
 
 	/* Link Information */
-	rc = snprintf(buf + len, max_size,
-			"\tdp_link:\n\t\ttest_requested = %d\n",
+	seq_printf(seq, "\tdp_link:\n\t\ttest_requested = %d\n",
 			debug->link->sink_request);
-	if (dp_debug_check_buffer_overflow(rc, &max_size, &len))
-		goto error;
-
-	rc = snprintf(buf + len, max_size,
-			"\t\tnum_lanes = %d\n",
+	seq_printf(seq, "\t\tnum_lanes = %d\n",
 			debug->link->link_params.num_lanes);
-	if (dp_debug_check_buffer_overflow(rc, &max_size, &len))
-		goto error;
-
 	link_params_rate = debug->link->link_params.rate;
-	rc = snprintf(buf + len, max_size,
-			"\t\tbw_code = %d\n",
+	seq_printf(seq, "\t\tbw_code = %d\n",
 			drm_dp_link_rate_to_bw_code(link_params_rate));
-	if (dp_debug_check_buffer_overflow(rc, &max_size, &len))
-		goto error;
-
 	lclk = debug->link->link_params.rate * 1000;
-	rc = snprintf(buf + len, max_size,
-			"\t\tlclk = %lld\n", lclk);
-	if (dp_debug_check_buffer_overflow(rc, &max_size, &len))
-		goto error;
-
-	rc = snprintf(buf + len, max_size,
-			"\t\tv_level = %d\n",
+	seq_printf(seq, "\t\tlclk = %lld\n", lclk);
+	seq_printf(seq, "\t\tv_level = %d\n",
 			debug->link->phy_params.v_level);
-	if (dp_debug_check_buffer_overflow(rc, &max_size, &len))
-		goto error;
-
-	rc = snprintf(buf + len, max_size,
-			"\t\tp_level = %d\n",
+	seq_printf(seq, "\t\tp_level = %d\n",
 			debug->link->phy_params.p_level);
-	if (dp_debug_check_buffer_overflow(rc, &max_size, &len))
-		goto error;
-
-	if (copy_to_user(user_buff, buf, len))
-		goto error;
-
-	*ppos += len;
 
-	kfree(buf);
-	return len;
- error:
-	kfree(buf);
-	return -EINVAL;
+	return 0;
 }
+DEFINE_SHOW_ATTRIBUTE(dp_debug);
 
 static int dp_test_data_show(struct seq_file *m, void *data)
 {
@@ -306,11 +198,6 @@ static int dp_test_active_open(struct inode *inode,
 			inode->i_private);
 }
 
-static const struct file_operations dp_debug_fops = {
-	.open = simple_open,
-	.read = dp_debug_read_info,
-};
-
 static const struct file_operations test_active_fops = {
 	.owner = THIS_MODULE,
 	.open = dp_test_active_open,