On Wednesday, November 6, 2019 12:56:56 AM CET Dmitry Torokhov wrote:
> Hi Rafael,
>
> On Wed, Nov 06, 2019 at 12:42:02AM +0100, Rafael J. Wysocki wrote:
> > On Wednesday, October 23, 2019 10:02:29 PM CET Dmitry Torokhov wrote:
> > > When copying/duplicating set of properties, move smaller properties that
> > > were stored separately directly inside property entry structures. We can
> > > move:
> > >
> > > - up to 8 bytes from U8 arrays
> > > - up to 4 words
> > > - up to 2 double words
> > > - one U64 value
> > > - one or 2 strings.
> >
> > Yes, we can do that, but how much of a difference does this really make?
>
> Arguably not much I think, but it was pretty cheap to do.
>
> >
> > Also, how can one distinguish between a single-value property and an inline
> > array which this change? By looking at the length?
>
> We do not really need to distinguish between the 2. The device
> properties API is typically wrap single values around arrays (i.e. it is
> perfectly fine to use scalar API to fetch first element of array and use
> array API to fetch a scalar). So we have property of certain type with
> certain number of elements, and it can either be stored inside
> property_entry structure, or outside of it. They are 2 orthogonal
> concepts.
>
> >
> > > Signed-off-by: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>
> > > ---
> > > drivers/base/swnode.c | 10 ++++++++++
> > > 1 file changed, 10 insertions(+)
> > >
> > > diff --git a/drivers/base/swnode.c b/drivers/base/swnode.c
> > > index 18a30fb3cc58..49e1108aa4b7 100644
> > > --- a/drivers/base/swnode.c
> > > +++ b/drivers/base/swnode.c
> > > @@ -280,6 +280,16 @@ static int property_entry_copy_data(struct property_entry *dst,
> > > if (!dst->name)
> > > goto out_free_data;
> > >
> > > + if (!dst->is_inline && dst->length <= sizeof(dst->value)) {
> > > + /* We have an opportunity to move the data inline */
> > > + const void *tmp = dst->pointer;
> > > +
> > > + memcpy(&dst->value, tmp, dst->length);
> > > + dst->is_inline = true;
> > > +
> > > + kfree(tmp);
> >
> > This would have been more useful if we had been able to avoid making the
> > allocation altogether.
>
> OK, I can do that and re-send this patch and the one with the tests.
But if you do that, IMO it would be prudent to extend the definition of
struct property_entry like this:
struct property_entry {
const char *name;
size_t length;
bool is_array;
enum dev_prop_type type;
union {
union {
const u8 *u8_data;
const u16 *u16_data;
const u32 *u32_data;
const u64 *u64_data;
const char * const *str;
} pointer;
union {
u8 u8_data;
u16 u16_data;
u32 u32_data;
u64 u64_data;
const char *str;
+ u8 u8_buf[sizeof(u64)];
+ u16 u16_buf[sizeof(u64)/sizeof(u16)];
+ u32 u32_buf[sizeof(u64)/sizeof(u32)];
+ char char_buf[sizeof(u64)];
} value;
};
};
to make it clear that the value field is going to be used as an array in
some cases.
> In the mean time, can you please consider patches 12-14?
I cannot find drivers/platform/x86/intel_cht_int33fe_typec.c in the mainline,
so I cannot apply patch [13/15] now and I'm not sure how useful it would be
to apply patches [10,12/15] without the other two.
