linux-kernel - [PATCH v3] media: rc: ir-spi: allocate buffer dynamically

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Message-ID: <20250609111715.2572138-1-demonsingur@gmail.com>
Date: Mon,  9 Jun 2025 14:17:13 +0300
From: Cosmin Tanislav <demonsingur@...il.com>
To: 
Cc: Sean Young <sean@...s.org>,
	Mauro Carvalho Chehab <mchehab@...nel.org>,
	linux-media@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Cosmin Tanislav <demonsingur@...il.com>
Subject: [PATCH v3] media: rc: ir-spi: allocate buffer dynamically

Replace the static transmit buffer with a dynamically allocated one,
removing the limit imposed on the number of pulses to transmit.

Calculate the number of pulses for each duration in the received buffer
ahead of time, while also adding up the total pulses, to be able to
allocate a buffer that perfectly fits the total number of pulses, then
populate it.

Signed-off-by: Cosmin Tanislav <demonsingur@...il.com>
---
V3:
 * move the allocation to be done per-TX operation

V2:
 * use devm_krealloc_array

 drivers/media/rc/ir-spi.c | 33 ++++++++++++++++++++-------------
 1 file changed, 20 insertions(+), 13 deletions(-)

diff --git a/drivers/media/rc/ir-spi.c b/drivers/media/rc/ir-spi.c
index 8fc8e496e6aa..50e30e2fae22 100644
--- a/drivers/media/rc/ir-spi.c
+++ b/drivers/media/rc/ir-spi.c
@@ -21,13 +21,11 @@
 #define IR_SPI_DRIVER_NAME		"ir-spi"
 
 #define IR_SPI_DEFAULT_FREQUENCY	38000
-#define IR_SPI_MAX_BUFSIZE		 4096
 
 struct ir_spi_data {
 	u32 freq;
 	bool negated;
 
-	u16 tx_buf[IR_SPI_MAX_BUFSIZE];
 	u16 pulse;
 	u16 space;
 
@@ -43,37 +41,42 @@ static int ir_spi_tx(struct rc_dev *dev, unsigned int *buffer, unsigned int coun
 	unsigned int len = 0;
 	struct ir_spi_data *idata = dev->priv;
 	struct spi_transfer xfer;
+	u16 *tx_buf;
 
 	/* convert the pulse/space signal to raw binary signal */
 	for (i = 0; i < count; i++) {
-		unsigned int periods;
+		buffer[i] = DIV_ROUND_CLOSEST(buffer[i] * idata->freq, 1000000);
+		len += buffer[i];
+	}
+
+	tx_buf = kmalloc_array(len, sizeof(*tx_buf), GFP_KERNEL);
+	if (!tx_buf)
+		return -ENOMEM;
+
+	len = 0;
+	for (i = 0; i < count; i++) {
 		int j;
 		u16 val;
 
-		periods = DIV_ROUND_CLOSEST(buffer[i] * idata->freq, 1000000);
-
-		if (len + periods >= IR_SPI_MAX_BUFSIZE)
-			return -EINVAL;
-
 		/*
 		 * The first value in buffer is a pulse, so that 0, 2, 4, ...
 		 * contain a pulse duration. On the contrary, 1, 3, 5, ...
 		 * contain a space duration.
 		 */
 		val = (i % 2) ? idata->space : idata->pulse;
-		for (j = 0; j < periods; j++)
-			idata->tx_buf[len++] = val;
+		for (j = 0; j < buffer[i]; j++)
+			tx_buf[len++] = val;
 	}
 
 	memset(&xfer, 0, sizeof(xfer));
 
 	xfer.speed_hz = idata->freq * 16;
-	xfer.len = len * sizeof(*idata->tx_buf);
-	xfer.tx_buf = idata->tx_buf;
+	xfer.len = len * sizeof(*tx_buf);
+	xfer.tx_buf = tx_buf;
 
 	ret = regulator_enable(idata->regulator);
 	if (ret)
-		return ret;
+		goto err_free_tx_buf;
 
 	ret = spi_sync_transfer(idata->spi, &xfer, 1);
 	if (ret)
@@ -81,6 +84,10 @@ static int ir_spi_tx(struct rc_dev *dev, unsigned int *buffer, unsigned int coun
 
 	regulator_disable(idata->regulator);
 
+err_free_tx_buf:
+
+	kfree(tx_buf);
+
 	return ret ? ret : count;
 }
 
-- 
2.49.0