On 29-07-24, 16:25, Pierre-Louis Bossart wrote:
>
>
> 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.
The fix seems right to me, we cannot have assumption that ports are
contagious, so we need to iterate over all valid ports and not to N
ports which code does now!
>
>
> > ---
> > 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];
> > }
--
~Vinod
