Hi! 2023-09-11 at 17:10, Andrew Davis wrote: > The DT binding for the reg-mux compatible states it can be used when the > "parent device of mux controller is not syscon device". It also allows > for a reg property. When the reg property is provided, use that to > identify the address space for this mux. If not provided fallback to > using the parent device as a regmap provider. > > Signed-off-by: Andrew Davis <afd@xxxxxx> > Reviewed-by: Nishanth Menon <nm@xxxxxx> > --- > > Changes from v2: > - Rebased on v6.6-rc1 > > Changes from v1: > - Flip logic as suggested in v1[0] > > [0] https://lore.kernel.org/lkml/1c27d9d4-b1cc-c158-90f7-f7e47e02c424@xxxxxx/T/ > > drivers/mux/mmio.c | 9 ++++++--- > 1 file changed, 6 insertions(+), 3 deletions(-) > > diff --git a/drivers/mux/mmio.c b/drivers/mux/mmio.c > index fd1d121a584ba..b6095b7853ed2 100644 > --- a/drivers/mux/mmio.c > +++ b/drivers/mux/mmio.c > @@ -44,10 +44,13 @@ static int mux_mmio_probe(struct platform_device *pdev) > int ret; > int i; > > - if (of_device_is_compatible(np, "mmio-mux")) > + if (of_device_is_compatible(np, "mmio-mux")) { > regmap = syscon_node_to_regmap(np->parent); > - else > - regmap = dev_get_regmap(dev->parent, NULL) ?: ERR_PTR(-ENODEV); > + } else { > + regmap = device_node_to_regmap(np); I started digging in device_node_to_regmap() to try to find an error that could be used to trigger if the failover to dev_get_regmap() should be tried, instead of always doing the failover on error. I got lost fairly quickly, but it seems device_node_to_regmap() can return -EDEFER_PROBE. While I'm not certain that it is applicable, that case should probably not fall back to dev_get_regmap()... Are there other error cases that should prevent the failover? I would guess that it's perhaps just a single error that should trigger trying the failover path? But I don't know, and which error if that's the case? How much badness can be caused if syscon_node_to_regmap() fails for some random obscure reason and the failover path is taken inadvertently? It certainly smells bad for -EDEFER_PROBE, but do you have any insight in other cases? And after getting to approx that point a while back, I had other things to take care of, and this fell off the table. Sorry! Cheers, Peter > + if (IS_ERR(regmap)) > + regmap = dev_get_regmap(dev->parent, NULL) ?: ERR_PTR(-ENODEV); > + } > if (IS_ERR(regmap)) { > ret = PTR_ERR(regmap); > dev_err(dev, "failed to get regmap: %d\n", ret);
