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Message-ID: <20231210113632.7880e730@jic23-huawei>
Date: Sun, 10 Dec 2023 11:36:32 +0000
From: Jonathan Cameron <jic23@...nel.org>
To: Marcus Folkesson <marcus.folkesson@...il.com>
Cc: Kent Gustavsson <kent@...oris.se>,
Lars-Peter Clausen <lars@...afoo.de>,
linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] iio: adc: mcp3911: simplify code with guard macro
On Wed, 06 Dec 2023 19:39:04 +0100
Marcus Folkesson <marcus.folkesson@...il.com> wrote:
> Use the guard(mutex) macro for handle mutex lock/unlocks.
>
> Signed-off-by: Marcus Folkesson <marcus.folkesson@...il.com>
Various changes inline - most are focused around simplifying the
path for any given flow through the code.
Rather than going for a v5 - I've applied this with the following diff on top
diff --git a/drivers/iio/adc/mcp3911.c b/drivers/iio/adc/mcp3911.c
index dfcb6cb7570f..7a32e7a1be9d 100644
--- a/drivers/iio/adc/mcp3911.c
+++ b/drivers/iio/adc/mcp3911.c
@@ -317,7 +317,7 @@ static int mcp3911_read_raw(struct iio_dev *indio_dev,
int *val2, long mask)
{
struct mcp3911 *adc = iio_priv(indio_dev);
- int ret = -EINVAL;
+ int ret;
guard(mutex)(&adc->lock);
switch (mask) {
@@ -331,17 +331,23 @@ static int mcp3911_read_raw(struct iio_dev *indio_dev,
return IIO_VAL_INT;
case IIO_CHAN_INFO_OFFSET:
ret = adc->chip->get_offset(adc, channel->channel, val);
- return (ret) ? ret : IIO_VAL_INT;
+ if (ret)
+ return ret;
+
+ return IIO_VAL_INT;
case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
ret = adc->chip->get_osr(adc, val);
- return (ret) ? ret : IIO_VAL_INT;
+ if (ret)
+ return ret;
+
+ return IIO_VAL_INT;
case IIO_CHAN_INFO_SCALE:
*val = mcp3911_scale_table[ilog2(adc->gain[channel->channel])][0];
*val2 = mcp3911_scale_table[ilog2(adc->gain[channel->channel])][1];
return IIO_VAL_INT_PLUS_NANO;
+ default:
+ return -EINVAL;
}
-
- return ret;
}
static int mcp3911_write_raw(struct iio_dev *indio_dev,
@@ -361,7 +367,7 @@ static int mcp3911_write_raw(struct iio_dev *indio_dev,
return adc->chip->set_scale(adc, channel->channel, i);
}
}
- break;
+ return -EINVAL;
case IIO_CHAN_INFO_OFFSET:
if (val2 != 0)
return -EINVAL;
@@ -373,9 +379,10 @@ static int mcp3911_write_raw(struct iio_dev *indio_dev,
return adc->chip->set_osr(adc, i);
}
}
- break;
+ return -EINVAL;
+ default:
+ return -EINVAL;
}
- return -EINVAL;
}
hope that's ok with you!
Jonathan
> ---
> Changes in v4:
> - Remove unreachable breaks
> - Link to v3: https://lore.kernel.org/r/20231205-mcp3911-guard-v3-1-df83e956d1e9@gmail.com
>
> Changes in v3:
> - Return early in good paths as well
> - Rebase against master
> - Link to v2: https://lore.kernel.org/r/20231127-mcp3911-guard-v2-1-9462630dca1e@gmail.com
>
> Changes in v2:
> - Return directly instead of goto label
> - Link to v1: https://lore.kernel.org/r/20231125-mcp3911-guard-v1-1-2748d16a3f3f@gmail.com
> ---
> drivers/iio/adc/mcp3911.c | 55 +++++++++++++----------------------------------
> 1 file changed, 15 insertions(+), 40 deletions(-)
>
> diff --git a/drivers/iio/adc/mcp3911.c b/drivers/iio/adc/mcp3911.c
> index d864558bc087..dfcb6cb7570f 100644
> --- a/drivers/iio/adc/mcp3911.c
> +++ b/drivers/iio/adc/mcp3911.c
> @@ -7,6 +7,7 @@
> */
> #include <linux/bitfield.h>
> #include <linux/bits.h>
> +#include <linux/cleanup.h>
> #include <linux/clk.h>
> #include <linux/delay.h>
> #include <linux/err.h>
> @@ -318,44 +319,28 @@ static int mcp3911_read_raw(struct iio_dev *indio_dev,
> struct mcp3911 *adc = iio_priv(indio_dev);
> int ret = -EINVAL;
>
> - mutex_lock(&adc->lock);
> + guard(mutex)(&adc->lock);
> switch (mask) {
> case IIO_CHAN_INFO_RAW:
> ret = mcp3911_read(adc,
> MCP3911_CHANNEL(channel->channel), val, 3);
> if (ret)
> - goto out;
> + return ret;
>
> *val = sign_extend32(*val, 23);
> -
> - ret = IIO_VAL_INT;
> - break;
> -
> + return IIO_VAL_INT;
> case IIO_CHAN_INFO_OFFSET:
> -
> ret = adc->chip->get_offset(adc, channel->channel, val);
> - if (ret)
> - goto out;
> -
> - ret = IIO_VAL_INT;
> - break;
> + return (ret) ? ret : IIO_VAL_INT;
Don't do this. The ternary just makes it harder to read.
if (ret)
return ret;
return IIO_VAL_INT;
+ the brackets around (ret) are unnecessary.
> case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
> ret = adc->chip->get_osr(adc, val);
> - if (ret)
> - goto out;
> -
> - ret = IIO_VAL_INT;
> - break;
> -
> + return (ret) ? ret : IIO_VAL_INT;
here as well
> case IIO_CHAN_INFO_SCALE:
> *val = mcp3911_scale_table[ilog2(adc->gain[channel->channel])][0];
> *val2 = mcp3911_scale_table[ilog2(adc->gain[channel->channel])][1];
> - ret = IIO_VAL_INT_PLUS_NANO;
> - break;
> + return IIO_VAL_INT_PLUS_NANO;
> }
>
> -out:
> - mutex_unlock(&adc->lock);
> return ret;
This ret is only reachable if we don't hit any of the switch entries so
better to add add a default and return -EINVAL to make that apparent and
let the compiler detect if we are missing a return earlier.
> }
>
> @@ -364,9 +349,8 @@ static int mcp3911_write_raw(struct iio_dev *indio_dev,
> int val2, long mask)
> {
> struct mcp3911 *adc = iio_priv(indio_dev);
> - int ret = -EINVAL;
>
> - mutex_lock(&adc->lock);
> + guard(mutex)(&adc->lock);
> switch (mask) {
> case IIO_CHAN_INFO_SCALE:
> for (int i = 0; i < MCP3911_NUM_SCALES; i++) {
> @@ -374,32 +358,24 @@ static int mcp3911_write_raw(struct iio_dev *indio_dev,
> val2 == mcp3911_scale_table[i][1]) {
>
> adc->gain[channel->channel] = BIT(i);
> - ret = adc->chip->set_scale(adc, channel->channel, i);
> + return adc->chip->set_scale(adc, channel->channel, i);
> }
> }
> break;
> case IIO_CHAN_INFO_OFFSET:
> - if (val2 != 0) {
> - ret = -EINVAL;
> - goto out;
> - }
> -
> - ret = adc->chip->set_offset(adc, channel->channel, val);
> - break;
> + if (val2 != 0)
> + return -EINVAL;
>
> + return adc->chip->set_offset(adc, channel->channel, val);
> case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
> for (int i = 0; i < ARRAY_SIZE(mcp3911_osr_table); i++) {
> if (val == mcp3911_osr_table[i]) {
> - ret = adc->chip->set_osr(adc, i);
> - break;
> + return adc->chip->set_osr(adc, i);
> }
> }
> break;
return -INVAL; here and similar above to simplify the flow.
> }
> -
> -out:
> - mutex_unlock(&adc->lock);
> - return ret;
> + return -EINVAL;
Move this to a default.
> }
>
> static int mcp3911_calc_scale_table(struct mcp3911 *adc)
> @@ -532,7 +508,7 @@ static irqreturn_t mcp3911_trigger_handler(int irq, void *p)
> int i = 0;
> int ret;
>
> - mutex_lock(&adc->lock);
> + guard(mutex)(&adc->lock);
> adc->tx_buf = MCP3911_REG_READ(MCP3911_CHANNEL(0), adc->dev_addr);
> ret = spi_sync_transfer(adc->spi, xfer, ARRAY_SIZE(xfer));
> if (ret < 0) {
> @@ -549,7 +525,6 @@ static irqreturn_t mcp3911_trigger_handler(int irq, void *p)
> iio_push_to_buffers_with_timestamp(indio_dev, &adc->scan,
> iio_get_time_ns(indio_dev));
> out:
> - mutex_unlock(&adc->lock);
> iio_trigger_notify_done(indio_dev->trig);
>
> return IRQ_HANDLED;
>
> ---
> base-commit: 33cc938e65a98f1d29d0a18403dbbee050dcad9a
> change-id: 20231125-mcp3911-guard-866591e2c947
>
> Best regards,
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