[v2,1/8] iio: core: Add opaque_struct_size() helper and use it
Commit Message
Introduce opaque_struct_size() helper, which may be moved
to overflow.h in the future, and use it in the IIO core.
Cc: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Nuno Sa <nuno.sa@analog.com>
---
drivers/iio/industrialio-core.c | 32 ++++++++++++++++++++++++--------
1 file changed, 24 insertions(+), 8 deletions(-)
Comments
On Fri, Jul 21, 2023 at 08:00:15PM +0300, Andy Shevchenko wrote:
> Introduce opaque_struct_size() helper, which may be moved
> to overflow.h in the future, and use it in the IIO core.
...
> +#define opaque_struct_size(p, a, s) ({ \
> + size_t _psize = sizeof(*(p)); \
> + size_t _asize = ALIGN(_psize, (a)); \
> + size_t _ssize = s; \
> + _ssize ? size_add(_asize, _ssize) : _psize; \
> +})
> +
> +#define opaque_struct_data(p, a) \
> + ((void *)(p) + ALIGN(sizeof(*(p)), (a)))
Hmm... This can potentially evaluate p twice.
Perhaps this variant is better:
#define opaque_struct_data(p, a) ALIGN((p) + 1, (a)))
Besides, I don't think we should worry about @s evaluation in the main macro
which may be simplified to
#define opaque_struct_size(p, a, s) \
((s) ? size_add(ALIGN(sizeof(*(p)), (a)), (s)) : sizeof(*(p)))
Thoughts?
On Fri, Jul 21, 2023 at 08:22:35PM +0300, Andy Shevchenko wrote:
> On Fri, Jul 21, 2023 at 08:00:15PM +0300, Andy Shevchenko wrote:
> > Introduce opaque_struct_size() helper, which may be moved
> > to overflow.h in the future, and use it in the IIO core.
...
> > +#define opaque_struct_size(p, a, s) ({ \
> > + size_t _psize = sizeof(*(p)); \
> > + size_t _asize = ALIGN(_psize, (a)); \
> > + size_t _ssize = s; \
> > + _ssize ? size_add(_asize, _ssize) : _psize; \
> > +})
> > +
> > +#define opaque_struct_data(p, a) \
> > + ((void *)(p) + ALIGN(sizeof(*(p)), (a)))
>
> Hmm... This can potentially evaluate p twice.
>
> Perhaps this variant is better:
>
> #define opaque_struct_data(p, a) ALIGN((p) + 1, (a)))
>
> Besides, I don't think we should worry about @s evaluation in the main macro
> which may be simplified to
>
> #define opaque_struct_size(p, a, s) \
> ((s) ? size_add(ALIGN(sizeof(*(p)), (a)), (s)) : sizeof(*(p)))
>
> Thoughts?
Also we may leave the struct always be aligned which makes the above even
simpler (but might waste bytes if @s = 0).
#define opaque_struct_size(p, a, s) size_add(ALIGN(sizeof(*(p)), (a)), (s))
(with the respective documentation update).
On Fri, Jul 21, 2023 at 08:25:12PM +0300, Andy Shevchenko wrote:
> On Fri, Jul 21, 2023 at 08:22:35PM +0300, Andy Shevchenko wrote:
> > On Fri, Jul 21, 2023 at 08:00:15PM +0300, Andy Shevchenko wrote:
> > > Introduce opaque_struct_size() helper, which may be moved
> > > to overflow.h in the future, and use it in the IIO core.
...
> > > +#define opaque_struct_size(p, a, s) ({ \
> > > + size_t _psize = sizeof(*(p)); \
> > > + size_t _asize = ALIGN(_psize, (a)); \
> > > + size_t _ssize = s; \
> > > + _ssize ? size_add(_asize, _ssize) : _psize; \
> > > +})
> > > +
> > > +#define opaque_struct_data(p, a) \
> > > + ((void *)(p) + ALIGN(sizeof(*(p)), (a)))
> >
> > Hmm... This can potentially evaluate p twice.
> >
> > Perhaps this variant is better:
> >
> > #define opaque_struct_data(p, a) ALIGN((p) + 1, (a)))
> >
> > Besides, I don't think we should worry about @s evaluation in the main macro
> > which may be simplified to
> >
> > #define opaque_struct_size(p, a, s) \
> > ((s) ? size_add(ALIGN(sizeof(*(p)), (a)), (s)) : sizeof(*(p)))
> >
> > Thoughts?
>
> Also we may leave the struct always be aligned which makes the above even
> simpler (but might waste bytes if @s = 0).
>
> #define opaque_struct_size(p, a, s) size_add(ALIGN(sizeof(*(p)), (a)), (s))
>
> (with the respective documentation update).
Jonathan, this patch can be skipped and if you are okay with the rest, the rest
may be (clearly, I have just checked) applied without as there is no dependency.
Hello Andy,
On Fri, Jul 21, 2023 at 08:25:12PM +0300, Andy Shevchenko wrote:
> On Fri, Jul 21, 2023 at 08:22:35PM +0300, Andy Shevchenko wrote:
> > On Fri, Jul 21, 2023 at 08:00:15PM +0300, Andy Shevchenko wrote:
> > > Introduce opaque_struct_size() helper, which may be moved
> > > to overflow.h in the future, and use it in the IIO core.
>
> ...
>
> > > +#define opaque_struct_size(p, a, s) ({ \
> > > + size_t _psize = sizeof(*(p)); \
> > > + size_t _asize = ALIGN(_psize, (a)); \
> > > + size_t _ssize = s; \
> > > + _ssize ? size_add(_asize, _ssize) : _psize; \
> > > +})
> > > +
> > > +#define opaque_struct_data(p, a) \
> > > + ((void *)(p) + ALIGN(sizeof(*(p)), (a)))
> >
> > Hmm... This can potentially evaluate p twice.
I don't think sizeof evaluates its parameter? It should only defer its
type and then calculate the respective size.
> > Perhaps this variant is better:
> >
> > #define opaque_struct_data(p, a) ALIGN((p) + 1, (a)))
Still I like this better.
> > Besides, I don't think we should worry about @s evaluation in the main macro
> > which may be simplified to
> >
> > #define opaque_struct_size(p, a, s) \
> > ((s) ? size_add(ALIGN(sizeof(*(p)), (a)), (s)) : sizeof(*(p)))
> >
> > Thoughts?
>
> Also we may leave the struct always be aligned which makes the above even
> simpler (but might waste bytes if @s = 0).
Depending on the value of a, the bytes "wasted" here might not be saved
anyhow because the memory allocator will round up the allocation size to
a multiple of some chunk size anyhow.
> #define opaque_struct_size(p, a, s) size_add(ALIGN(sizeof(*(p)), (a)), (s))
>
> (with the respective documentation update).
That would be my favourite.
Possible users of this helper include:
__spi_alloc_controller() in drivers/spi/spi.c
alloc_netdev_mqs in net/core/dev.c
Best regards
Uwe
@@ -1617,6 +1617,28 @@ const struct device_type iio_device_type = {
.release = iio_dev_release,
};
+/**
+ * opaque_struct_size() - Calculate size of opaque structure with trailing aligned data.
+ * @p: Pointer to the opaque structure.
+ * @a: Alignment in bytes before trailing data.
+ * @s: Data size in bytes (can be 0).
+ *
+ * Calculates size of memory needed for structure of @p followed by the aligned data
+ * of size @s. When @s is 0, the alignment @a is not taken into account and the result
+ * is an equivalent to sizeof(*(@p)).
+ *
+ * Returns: Number of bytes needed or SIZE_MAX on overflow.
+ */
+#define opaque_struct_size(p, a, s) ({ \
+ size_t _psize = sizeof(*(p)); \
+ size_t _asize = ALIGN(_psize, (a)); \
+ size_t _ssize = s; \
+ _ssize ? size_add(_asize, _ssize) : _psize; \
+})
+
+#define opaque_struct_data(p, a) \
+ ((void *)(p) + ALIGN(sizeof(*(p)), (a)))
+
/**
* iio_device_alloc() - allocate an iio_dev from a driver
* @parent: Parent device.
@@ -1628,19 +1650,13 @@ struct iio_dev *iio_device_alloc(struct device *parent, int sizeof_priv)
struct iio_dev *indio_dev;
size_t alloc_size;
- alloc_size = sizeof(struct iio_dev_opaque);
- if (sizeof_priv) {
- alloc_size = ALIGN(alloc_size, IIO_DMA_MINALIGN);
- alloc_size += sizeof_priv;
- }
-
+ alloc_size = opaque_struct_size(iio_dev_opaque, IIO_DMA_MINALIGN, sizeof_priv);
iio_dev_opaque = kzalloc(alloc_size, GFP_KERNEL);
if (!iio_dev_opaque)
return NULL;
indio_dev = &iio_dev_opaque->indio_dev;
- indio_dev->priv = (char *)iio_dev_opaque +
- ALIGN(sizeof(struct iio_dev_opaque), IIO_DMA_MINALIGN);
+ indio_dev->priv = opaque_struct_data(iio_dev_opaque, IIO_DMA_MINALIGN);
indio_dev->dev.parent = parent;
indio_dev->dev.type = &iio_device_type;