Re: [PATCH v3 10/15] iio: resolver: ad2s1210: use bitmap_write
From: David Lechner <dlechner@baylibre.com>
Date: 2025-02-20 20:54:56
Also in:
linux-gpio, linux-iio, linux-mmc, linux-phy, linux-sound, lkml
Subsystem:
analog devices inc iio drivers, iio subsystem and drivers, the rest · Maintainers:
Nuno Sá, Michael Hennerich, Jonathan Cameron, Linus Torvalds
On 2/10/25 4:33 PM, David Lechner wrote:
quoted hunk ↗ jump to hunk
Replace bitmap array access with bitmap_write. Accessing the bitmap array directly is not recommended and now there is a helper function that can be used. Reviewed-by: Linus Walleij <redacted> Signed-off-by: David Lechner <dlechner@baylibre.com> --- drivers/iio/resolver/ad2s1210.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)diff --git a/drivers/iio/resolver/ad2s1210.c b/drivers/iio/resolver/ad2s1210.c index 7f18df790157f1e411fb70de193a49f0677c999f..04879e6d538bce664469c5f6759d8b1cedea16e9 100644 --- a/drivers/iio/resolver/ad2s1210.c +++ b/drivers/iio/resolver/ad2s1210.c@@ -46,6 +46,7 @@ */ #include <linux/bitfield.h> +#include <linux/bitmap.h> #include <linux/bits.h> #include <linux/cleanup.h> #include <linux/clk.h>@@ -180,7 +181,7 @@ static int ad2s1210_set_mode(struct ad2s1210_state *st, enum ad2s1210_mode mode) if (!gpios) return mode == st->fixed_mode ? 0 : -EOPNOTSUPP; - bitmap[0] = mode; + bitmap_write(bitmap, mode, 0, 2); return gpiod_multi_set_value_cansleep(gpios, bitmap); }@@ -1470,7 +1471,7 @@ static int ad2s1210_setup_gpios(struct ad2s1210_state *st) return dev_err_probe(dev, -EINVAL, "requires exactly 2 resolution-gpios\n"); - bitmap[0] = st->resolution; + bitmap_write(bitmap, st->resolution, 0, 2); ret = gpiod_multi_set_value_cansleep(resolution_gpios, bitmap); if (ret < 0)
There is actually a bug here pointed out in a similar patch. bitmap_write() only modifies the bitmap, so this introduces an unintialized use bug. [1] Here, we only use the bits that we set, so runtime behavior would not actually be buggy but still best to fully initialize the memory. I'm a bit surprised that my local compiler and iio/testing both didn't catch that since GCC 14 caught it in the other driver. [1]: https://lore.kernel.org/linux-gpio/20250217132152.29d86d6c@jic23-huawei/T/#m3163d2c5db5b7376504d8ad6f23716f1119de761 (local) The fix is simple, we can zero-initialize the bitmap.
diff --git a/drivers/iio/resolver/ad2s1210.c b/drivers/iio/resolver/ad2s1210.c
index 04879e6d538b..ab860cedecd1 100644
--- a/drivers/iio/resolver/ad2s1210.c
+++ b/drivers/iio/resolver/ad2s1210.c@@ -176,7 +176,7 @@ struct ad2s1210_state { static int ad2s1210_set_mode(struct ad2s1210_state *st, enum ad2s1210_mode mode) { struct gpio_descs *gpios = st->mode_gpios; - DECLARE_BITMAP(bitmap, 2); + DECLARE_BITMAP(bitmap, 2) = { }; if (!gpios) return mode == st->fixed_mode ? 0 : -EOPNOTSUPP;
@@ -1427,7 +1427,7 @@ static int ad2s1210_setup_gpios(struct ad2s1210_state *st) struct device *dev = &st->sdev->dev; struct gpio_descs *resolution_gpios; struct gpio_desc *reset_gpio; - DECLARE_BITMAP(bitmap, 2); + DECLARE_BITMAP(bitmap, 2) = { }; int ret; /* should not be sampling on startup */