Re: [PATCH 01/13] acpi: utils: Cleanup acpi_dev_match_cb

From: Suzuki K Poulose
Date: Thu Jun 06 2019 - 05:25:49 EST

Hi Rafael,

On 06/06/2019 10:14, Rafael J. Wysocki wrote:
On Wed, Jun 5, 2019 at 5:14 PM Suzuki K Poulose <suzuki.poulose@xxxxxxx> wrote:

acpi_dev_match_cb match function modifies the "data" argument
to pass on a result which could be easily deduced from the result
of the bus_find_device() call at the caller site. Clean this
up in preparation to convert the "match" argument for bus_find_device
to accept a "const" data pointer, similar to class_find_device. This
would allow consolidating the match routines for these two APIs.

This changelog can be improved IMO.

I agree. Will update it.

In fact, the final goal here is to pass (const void *) as the second
argument to acpi_dev_match_cb() (which you could do right away in this
patch if I'm not mistaken) which is because you want to modify the
prototype of bus_find_device().

So why don't you write something like this in the changelog:

"The prototype of bus_find_device() will be unified with that of
class_find_device() subsequently, but for this purpose the callback
functions passed to it need to take (const void *) as the second
argument. Consequently, they cannot modify the memory pointed to by
that argument which currently is not the case for acpi_dev_match_cb().
However, acpi_dev_match_cb() really need not modify the "match" object
passed to it, because acpi_dev_get_first_match_dev() which uses it via
bus_find_device() can easily convert the result of bus_find_device()
into the pointer to return.


For this reason, update acpi_dev_match_cb() to avoid the redundant
memory updates and change the type of its second argument to (const
void *)."

We can't do that quite yet, until we unify the prototype of the

Cc: "Rafael J. Wysocki" <rjw@xxxxxxxxxxxxx>
Cc: Len Brown <lenb@xxxxxxxxxx>
Cc: linux-acpi@xxxxxxxxxxxxxxx
Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
drivers/acpi/utils.c | 7 +------
1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/drivers/acpi/utils.c b/drivers/acpi/utils.c
index 7def63a..1391b63 100644
--- a/drivers/acpi/utils.c
+++ b/drivers/acpi/utils.c
@@ -725,8 +725,6 @@ bool acpi_dev_found(const char *hid)

struct acpi_dev_match_info {
- const char *dev_name;
- struct acpi_device *adev;
struct acpi_device_id hid[2];
const char *uid;
s64 hrv;
@@ -746,9 +744,6 @@ static int acpi_dev_match_cb(struct device *dev, void *data)

And why not to change the type of the second arg to "const void *data" here?

Because, that would conflict with what bus_find_device() expects now. We make
the change only later. Since this change was a bit more intrusive than simply
changing the type of the parameter, I kept it as a preparatory patch.

Thanks for the review !