Re: [PATCH v2 3/3] usb: typec: tcpm: Get Sink VDO from fwnode

On 1/31/21 9:11 PM, Kyle Tso wrote:

On Mon, Feb 1, 2021 at 12:02 AM Guenter Roeck [off-list ref] wrote:

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On 1/31/21 7:18 AM, Kyle Tso wrote:

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Commit a079973f462a ("usb: typec: tcpm: Remove tcpc_config
configuration mechanism") removed the tcpc_config which includes the
Sink VDO and it is not yet added back with fwnode. Add it now.

Signed-off-by: Kyle Tso <redacted>
---
Changes since v1:
- updated the commit message

 drivers/usb/typec/tcpm/tcpm.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
index 403a483645dd..84c8a52f8af1 100644
--- a/drivers/usb/typec/tcpm/tcpm.c
+++ b/drivers/usb/typec/tcpm/tcpm.c

@@ -5677,6 +5677,18 @@ static int tcpm_fw_get_caps(struct tcpm_port *port,
                      port->new_source_frs_current = frs_current;
      }

+     ret = fwnode_property_read_u32_array(fwnode, "sink-vdos", NULL, 0);

fwnode_property_count_u32(), maybe ?

That's the same and looks like fwnode_property_count_u32 is better to read.
I will revise it in the next version.

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+     if (ret <= 0 && ret != -EINVAL) {
+             return -EINVAL;

Why return any error except -EINVAL (including return values of 0) as -EINVAL,
and -EINVAL as no error ?

sink-vdos is not a mandatory property which means -EINVAL is acceptable.

If the return < 0 and the value is not -EINVAL, it means that the
error is other than "not present" in the device tree.
If the return == 0, it means that the sink-vdos is present in the
device tree but no value inside it.

I think that should return -ENODATA. Not sure if/when it would actually return 0.

Both of the above situations are not acceptable.

Personally I would prefer that a bit more explicit in the code, ie
handle errors first and drop the else statement below. But maybe
that is just me.

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+     } else if (ret > 0) {
+             port->nr_snk_vdo = min(ret, VDO_MAX_OBJECTS);
+             ret = fwnode_property_read_u32_array(fwnode, "sink-vdos",
+                                                  port->snk_vdo,
+                                                  port->nr_snk_vdo);
+             if (ret < 0)
+                     return -EINVAL;

static analyzer code used to complain about overriding error codes.
Not sure if that is still true. Either case, why not return the
original error ?

Returning the original error codes is good. I just followed the return
value of other error handling in this function.
will revise it in the next version.

Never mind, with the rest of the code being similar I guess that either
static analyzers gave up complaining or they already have a field day
anyway.

Thanks,
Guenter

Thanks,
Kyle

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Thanks,
Guenter

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+     }
+
      return 0;
 }