linux-kernel - [PATCH] usb: dwc2: Use seq_buf instead of hand writing it

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Date:   Sat, 28 Oct 2023 12:41:02 +0200
From:   Christophe JAILLET <christophe.jaillet@...adoo.fr>
To:     Minas Harutyunyan <hminas@...opsys.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        linux-usb@...r.kernel.org
Subject: [PATCH] usb: dwc2: Use seq_buf instead of hand writing it

cat_printf() re-implements what the seq_buf API does.
So, switch to the seq_buf API to save some line of code.

Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
---
seq_buf_printf(&buf, ", "); could be seq_buf_puts(), but the result could
be slightly different. So I kept a conservative approach.

If only some seq_buf_printf() are used, the final seq_buf_terminate() can
be avoided, but I think it is cleaner with it.
---
 drivers/usb/dwc2/hcd_queue.c | 53 ++++++++----------------------------
 1 file changed, 11 insertions(+), 42 deletions(-)

diff --git a/drivers/usb/dwc2/hcd_queue.c b/drivers/usb/dwc2/hcd_queue.c
index 0d4495c6b9f7..66fb74a70bdd 100644
--- a/drivers/usb/dwc2/hcd_queue.c
+++ b/drivers/usb/dwc2/hcd_queue.c
@@ -18,6 +18,7 @@
 #include <linux/io.h>
 #include <linux/slab.h>
 #include <linux/usb.h>
+#include <linux/seq_buf.h>
 
 #include <linux/usb/hcd.h>
 #include <linux/usb/ch11.h>
@@ -359,41 +360,6 @@ static unsigned long *dwc2_get_ls_map(struct dwc2_hsotg *hsotg,
 }
 
 #ifdef DWC2_PRINT_SCHEDULE
-/*
- * cat_printf() - A printf() + strcat() helper
- *
- * This is useful for concatenating a bunch of strings where each string is
- * constructed using printf.
- *
- * @buf:   The destination buffer; will be updated to point after the printed
- *         data.
- * @size:  The number of bytes in the buffer (includes space for '\0').
- * @fmt:   The format for printf.
- * @...:   The args for printf.
- */
-static __printf(3, 4)
-void cat_printf(char **buf, size_t *size, const char *fmt, ...)
-{
-	va_list args;
-	int i;
-
-	if (*size == 0)
-		return;
-
-	va_start(args, fmt);
-	i = vsnprintf(*buf, *size, fmt, args);
-	va_end(args);
-
-	if (i >= *size) {
-		(*buf)[*size - 1] = '\0';
-		*buf += *size;
-		*size = 0;
-	} else {
-		*buf += i;
-		*size -= i;
-	}
-}
-
 /*
  * pmap_print() - Print the given periodic map
  *
@@ -417,8 +383,7 @@ static void pmap_print(unsigned long *map, int bits_per_period,
 
 	for (period = 0; period < periods_in_map; period++) {
 		char tmp[64];
-		char *buf = tmp;
-		size_t buf_size = sizeof(tmp);
+		struct seq_buf buf;
 		int period_start = period * bits_per_period;
 		int period_end = period_start + bits_per_period;
 		int start = 0;
@@ -426,6 +391,8 @@ static void pmap_print(unsigned long *map, int bits_per_period,
 		bool printed = false;
 		int i;
 
+		seq_buf_init((&s, tmp, sizeof(tmp));
+
 		for (i = period_start; i < period_end + 1; i++) {
 			/* Handle case when ith bit is set */
 			if (i < period_end &&
@@ -442,17 +409,19 @@ static void pmap_print(unsigned long *map, int bits_per_period,
 				continue;
 
 			if (!printed)
-				cat_printf(&buf, &buf_size, "%s %d: ",
-					   period_name, period);
+				seq_buf_printf(&buf, "%s %d: ", period_name,
+					       period);
 			else
-				cat_printf(&buf, &buf_size, ", ");
+				seq_buf_printf(&buf, ", ");
 			printed = true;
 
-			cat_printf(&buf, &buf_size, "%d %s -%3d %s", start,
-				   units, start + count - 1, units);
+			seq_buf_printf(&buf, "%d %s -%3d %s", start, units,
+				       start + count - 1, units);
 			count = 0;
 		}
 
+		seq_buf_terminate(&s);
+
 		if (printed)
 			print_fn(tmp, print_data);
 	}
-- 
2.34.1