| Message ID | d17bd9b622dbe3f7cb2f18736ef3138a6927f86c.1700986053.git.christophe.jaillet@wanadoo.fr (mailing list archive) |
|---|---|
| State | Changes Requested |
| Headers | show |
| Series | [1/2] mux: Turn 'mux' into a flexible array in 'struct mux_chip' | expand |
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@wanadoo.fr> > --- > 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)
On Sun, Nov 26, 2023 at 09:08:11AM +0100, 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@wanadoo.fr> > --- > 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). Once people start using size_add() then we'll get used to reading it. The controllers value comes from device tree. For example, in mux_mmio_probe(). ret = of_property_count_u32_elems(np, "mux-reg-masks"); I should make Smatch parse device trees. So that it will know the correct range for ret in that assignment. Eventually, I will. KTODO: make Smatch understand device tree values regards, dan carpenter
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)
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@wanadoo.fr> --- 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). --- drivers/mux/core.c | 4 +--- include/linux/mux/driver.h | 5 +++-- 2 files changed, 4 insertions(+), 5 deletions(-)