On 11/26/23 02:08, Christophe JAILLET wrote:
The 'mux' array stored in 'struct mux_chip' can be changed into a flexible
array.
This saves:
- a pointer in the structure
- an indirection when accessing the array
- some pointer arithmetic when computing and storing the address in
'mux'
It is also now possible to use __counted_by() and struct_size() for
additional safety.
The address for the 'priv' memory is computed with mux_chip_priv(). It
should work as good with a flexible array.
Signed-off-by: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>
---
The struct_size() goodies only work if sizeof_priv is 0. Adding an
additional size_add() would make it safe in all cases but would make code
less readable (IMHO).
Just save struct_size() in another variable, and use size_add() like this:
size_t size = struct_size(..);
.. kzalloc(size_add(size, sizeof_priv), ...);
--
Gustavo
---
drivers/mux/core.c | 4 +---
include/linux/mux/driver.h | 5 +++--
2 files changed, 4 insertions(+), 5 deletions(-)
diff --git a/drivers/mux/core.c b/drivers/mux/core.c
index 775816112932..80b2607b083b 100644
--- a/drivers/mux/core.c
+++ b/drivers/mux/core.c
@@ -98,13 +98,11 @@ struct mux_chip *mux_chip_alloc(struct device *dev,
if (WARN_ON(!dev || !controllers))
return ERR_PTR(-EINVAL);
- mux_chip = kzalloc(sizeof(*mux_chip) +
- controllers * sizeof(*mux_chip->mux) +
+ mux_chip = kzalloc(struct_size(mux_chip, mux, controllers) +
sizeof_priv, GFP_KERNEL);
if (!mux_chip)
return ERR_PTR(-ENOMEM);
- mux_chip->mux = (struct mux_control *)(mux_chip + 1);
mux_chip->dev.class = &mux_class;
mux_chip->dev.type = &mux_type;
mux_chip->dev.parent = dev;
diff --git a/include/linux/mux/driver.h b/include/linux/mux/driver.h
index 18824064f8c0..c29e9b7fb17b 100644
--- a/include/linux/mux/driver.h
+++ b/include/linux/mux/driver.h
@@ -56,18 +56,19 @@ struct mux_control {
/**
* struct mux_chip - Represents a chip holding mux controllers.
* @controllers: Number of mux controllers handled by the chip.
- * @mux: Array of mux controllers that are handled.
* @dev: Device structure.
* @id: Used to identify the device internally.
* @ops: Mux controller operations.
+ * @mux: Array of mux controllers that are handled.
*/
struct mux_chip {
unsigned int controllers;
- struct mux_control *mux;
struct device dev;
int id;
const struct mux_control_ops *ops;
+
+ struct mux_control mux[] __counted_by(controllers);
};
#define to_mux_chip(x) container_of((x), struct mux_chip, dev)
