On 7/29/24 16:01, Krzysztof Kozlowski wrote:
> Two bitmasks in 'struct sdw_slave_prop' - 'source_ports' and
> 'sink_ports' - define which ports to program in
> sdw_program_slave_port_params(). The masks are used to get the
> appropriate data port properties ('struct sdw_get_slave_dpn_prop') from
> an array.
>
> Bitmasks can be non-continuous or can start from index different than 0,
> thus when looking for matching port property for given port, we must
> iterate over mask bits, not from 0 up to number of ports.
>
> This fixes allocation and programming slave ports, when a source or sink
> masks start from further index.
>
> Fixes: f8101c74aa54 ("soundwire: Add Master and Slave port programming")
> Cc: <stable@xxxxxxxxxxxxxxx>
> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx>
This is a valid change to optimize how the port are accessed.
But the commit message is not completely clear, the allocation in
mipi_disco.c is not modified and I don't think there's anything that
would crash. If there are non-contiguous ports, we will still allocate
space that will not be initialized/used.
/* Allocate memory for set bits in port lists */
nval = hweight32(prop->source_ports);
prop->src_dpn_prop = devm_kcalloc(&slave->dev, nval,
sizeof(*prop->src_dpn_prop),
GFP_KERNEL);
if (!prop->src_dpn_prop)
return -ENOMEM;
/* Read dpn properties for source port(s) */
sdw_slave_read_dpn(slave, prop->src_dpn_prop, nval,
prop->source_ports, "source");
IOW, this is a valid change, but it's an optimization, not a fix in the
usual sense of 'kernel oops otherwise'.
Am I missing something?
BTW, the notion of DPn is that n > 0. DP0 is a special case with
different properties, BIT(0) cannot be set for either of the sink/source
port bitmask.
> ---
> drivers/soundwire/stream.c | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/soundwire/stream.c b/drivers/soundwire/stream.c
> index 7aa4900dcf31..f275143d7b18 100644
> --- a/drivers/soundwire/stream.c
> +++ b/drivers/soundwire/stream.c
> @@ -1291,18 +1291,18 @@ struct sdw_dpn_prop *sdw_get_slave_dpn_prop(struct sdw_slave *slave,
> unsigned int port_num)
> {
> struct sdw_dpn_prop *dpn_prop;
> - u8 num_ports;
> + unsigned long mask;
> int i;
>
> if (direction == SDW_DATA_DIR_TX) {
> - num_ports = hweight32(slave->prop.source_ports);
> + mask = slave->prop.source_ports;
> dpn_prop = slave->prop.src_dpn_prop;
> } else {
> - num_ports = hweight32(slave->prop.sink_ports);
> + mask = slave->prop.sink_ports;
> dpn_prop = slave->prop.sink_dpn_prop;
> }
>
> - for (i = 0; i < num_ports; i++) {
> + for_each_set_bit(i, &mask, 32) {
> if (dpn_prop[i].num == port_num)
> return &dpn_prop[i];
> }
