[U-Boot] [PATCH v2] net/eth.c: fix eth_write_hwaddr() to use dev->enetaddr as fall back

Dirk Behme
2012-02-08T07:13:10Z

On 23.01.2012 17:17, Simon Glass wrote:
> Hi Dirk,
>
> On Jan 23, 2012 12:30 AM, "Dirk Behme" <dirk.behme@de.bosch.com
> <mailto:dirk.behme@de.bosch.com>> wrote:
> >
> > On 23.01.2012 08:31, Simon Glass wrote:
> >>
> >> Hi,
> >>
> >> On Thu, Jan 19, 2012 at 12:56 AM, Dirk Behme
> <dirk.behme at de.bosch.com <mailto:dirk.behme@de.bosch.com>> wrote:
> >>>
> >>> From: Eric Miao <eric.miao at linaro.org <mailto:eric.miao@linaro.org>>
> >>>
> >>> Ignore the return value of eth_getenv_enetaddr_by_index(), and if it
> >>> fails, fall back to use dev->enetaddr, which could be filled up by
> >>> the ethernet device driver:
> >>>
> >>> With the current code, introduced with below commit, eth_write_hwaddr()
> >>> will fail immediately if there is no eth<n>addr in the environment
> variables.
> >>>
> >>> However, e.g. for an overo based product that uses the SMSC911x
> ethernet
> >>> chip (with the MAC address set via EEPROM connected to the SMSC911x
> chip),
> >>> the MAC address is still OK.
> >>>
> >>> On mx28 boards that are depending on the OCOTP bits to set the MAC
> address
> >>> (like the Denx m28 board), the OCOTP bits should be used instead of
> >>> failing on the environment variables.
> >>>
> >>> Actually, this was the original behavior, and was later changed by
> >>> commit 7616e7850804c7c69e0a22c179dfcba9e8f3f587.
> >>>
> >>> Signed-off-by: Eric Miao <eric.miao@linaro.org
> <mailto:eric.miao@linaro.org>>
> >>> Acked-by: Simon Glass <sjg at chromium.org <mailto:sjg@chromium.org>>
> >>> Acked-by: Dirk Behme <dirk.behme@de.bosch.com
> <mailto:dirk.behme@de.bosch.com>>
> >>> CC: Stefan Roese <sr at denx.de <mailto:sr@denx.de>>
> >>> CC: Eric Miao <eric.miao at linaro.org <mailto:eric.miao@linaro.org>>
> >>> CC: Wolfgang Denk <wd at denx.de <mailto:wd@denx.de>>
> >>> CC: Philip Balister <philip at balister.org <mailto:philip@balister.org>>
> >>> CC: Zach Sadecki <zach at itwatchdogs.com <mailto:zach@itwatchdogs.com>>
> >>> ---
> >>> v2: Correct the referenced commit ID and update the commit message.
> >>> No functional change at the code itself.
> >>>
> >>> Note: This resend is based on my understanding from
> >>>
> >>> http://lists.denx.de/pipermail/u-boot/2012-January/116118.html
> >>>
> >>> Please let Eric and me know if I missed anything there.
> >>
> >>
> >> I don't think you have missed anything and I have already acked this.
> >> But I want to start a related discussion.
> >>
> >> The code structure does bug me a bit - I think it is too confusing.
> >> eth_getenv_enetaddr() returns an error if there is no environment
> >> variable set or if the address it gets from the environment variable
> >> is invalid. We should probably not conflate those two. The first is ok
> >> here, but the second isn't, I think.
> >>
> >> What if the driver has no write_hwaddr method? Do we silently ignore
> >> the environment variable value?
> >>
> >> Why use memcmp() against env_enetaddr when the function we just called
> >> returns an error that tells us whether it is supposed to be valid (the
> >> error return your patch squashes)?
> >>
> >> We set the hwaddr by writing directly into the dev->enet_addr field
> >> and then calling write_hwaddr() if it exists. Maybe that is ok - is
> >> the lack of write_hwaddr() an indication that the driver does MAC
> >> address handling on the fly, or just that it can't set the MAC address
> >> at all?
> >>
> >> Overall I feel that eth_write_hwaddr() should return success or
> >> failure, confident in its determination that there is either a valid
> >> MAC address or there is not. The message you are seeing is I suppose
> >> an indication that it thinks there is a problem, when in fact none
> >> exists in this case. At the moment it feels fragile.
> >>
> >> I wonder whether a little refactor here would be best?
> >>
> >> That said, your patch restores the original behaviour, hiding the
> >> problem which isn't actually a problem in this case, and which we
> >> don't want to report. So it is better than the status quo.
> >
> >
> > Ok, thanks.
> >
> > I'm not an expert for this code, nor is the patch from me. It's from
> Eric ;) I just try to help to mainline all the stuff we have collected
> for i.MX6.
> >
> > Therefore I wonder if it would be possible to split this into two steps:
> >
> > a) Improve the status quo by applying this patch
> > b) In parallel discuss how to refactor and improve this code as you
> describe above
> >
> > It's my feeling that with (a) we still have a chance to improve
> v2012.03. But I doubt that (b) would make it into v2012.03.
>
> Yes agreed, it is a separate discussion. I added Wolfgang on cc to see
> what he thinks.

Any news to this?

Many thanks

Dirk