staging:iio:ad7280a: Do not store transfer buffer on the stack

Some I2C controllers may not be able to handle transfer buffers that are placed
on the stack.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

diff --git a/drivers/staging/iio/adc/ad7280a.c b/drivers/staging/iio/adc/ad7280a.c
index 89ee65bdc279d6839ea4464035a21fb7ffed7693..1ac11f64827c73de9260ebeb78066eef1b28f09f 100644 (file)
--- a/drivers/staging/iio/adc/ad7280a.c
+++ b/drivers/staging/iio/adc/ad7280a.c
@@ -134,6 +134,8 @@ struct ad7280_state {
        unsigned char                   aux_threshhigh;
        unsigned char                   aux_threshlow;
        unsigned char                   cb_mask[AD7280A_MAX_CHAIN];
+
+       __be32                          buf[2] ____cacheline_aligned;
 };
 
 static void ad7280_crc8_build_table(unsigned char *crc_tab)
@@ -189,22 +191,22 @@ static void ad7280_delay(struct ad7280_state *st)
                msleep(1);
 }
 
-static int __ad7280_read32(struct spi_device *spi, unsigned *val)
+static int __ad7280_read32(struct ad7280_state *st, unsigned *val)
 {
-       __be32 rx_buf, tx_buf = cpu_to_be32(AD7280A_READ_TXVAL);
        int ret;
-
        struct spi_transfer t = {
-               .tx_buf = &tx_buf,
-               .rx_buf = &rx_buf,
+               .tx_buf = &st->buf[0],
+               .rx_buf = &st->buf[1],
                .len = 4,
        };
 
-       ret = spi_sync_transfer(spi, &t, 1);
+       st->buf[0] = cpu_to_be32(AD7280A_READ_TXVAL);
+
+       ret = spi_sync_transfer(st->spi, &t, 1);
        if (ret)
                return ret;
 
-       *val = be32_to_cpu(rx_buf);
+       *val = be32_to_cpu(st->buf[1]);
 
        return 0;
 }
@@ -214,12 +216,11 @@ static int ad7280_write(struct ad7280_state *st, unsigned devaddr,
 {
        unsigned reg = (devaddr << 27 | addr << 21 |
                        (val & 0xFF) << 13 | all << 12);
-       __be32 tx_buf;
 
        reg |= ad7280_calc_crc8(st->crc_tab, reg >> 11) << 3 | 0x2;
-       tx_buf = cpu_to_be32(reg);
+       st->buf[0] = cpu_to_be32(reg);
 
-       return spi_write(st->spi, &tx_buf, 4);
+       return spi_write(st->spi, &st->buf[0], 4);
 }
 
 static int ad7280_read(struct ad7280_state *st, unsigned devaddr,
@@ -249,7 +250,7 @@ static int ad7280_read(struct ad7280_state *st, unsigned devaddr,
        if (ret)
                return ret;
 
-       __ad7280_read32(st->spi, &tmp);
+       __ad7280_read32(st, &tmp);
 
        if (ad7280_check_crc(st, tmp))
                return -EIO;
@@ -287,7 +288,7 @@ static int ad7280_read_channel(struct ad7280_state *st, unsigned devaddr,
 
        ad7280_delay(st);
 
-       __ad7280_read32(st->spi, &tmp);
+       __ad7280_read32(st, &tmp);
 
        if (ad7280_check_crc(st, tmp))
                return -EIO;
@@ -320,7 +321,7 @@ static int ad7280_read_all_channels(struct ad7280_state *st, unsigned cnt,
        ad7280_delay(st);
 
        for (i = 0; i < cnt; i++) {
-               __ad7280_read32(st->spi, &tmp);
+               __ad7280_read32(st, &tmp);
 
                if (ad7280_check_crc(st, tmp))
                        return -EIO;
@@ -363,7 +364,7 @@ static int ad7280_chain_setup(struct ad7280_state *st)
                return ret;
 
        for (n = 0; n <= AD7280A_MAX_CHAIN; n++) {
-               __ad7280_read32(st->spi, &val);
+               __ad7280_read32(st, &val);
                if (val == 0)
                        return n - 1;