Re: [PATCH] net:fec: fixed unaligned access and stack corruption

[Marco Felsch <m.felsch@pengutronix.de>]

Hi,

sorry for jumping in.

On 20-07-11 07:28, Ahmad Fatoum wrote:
> Hi,
> 
> On 7/11/20 7:20 AM, Sascha Hauer wrote:
> > On Sat, Jul 11, 2020 at 07:13:11AM +0200, Ahmad Fatoum wrote:
> >>
> >>
> >> On 7/11/20 7:07 AM, Sascha Hauer wrote:
> >>> On Tue, Jul 07, 2020 at 07:11:31PM +0200, Ahmad Fatoum wrote:
> >>>> On 7/7/20 6:01 PM, Enrico Scholz wrote:
> >>>>> on 64 bit architectures, the 'enum fec_type' might not be aligned and
> >>>>> large enough to hold a pointer.  
> >>>>
> >>>> I am wondering if we couldn't just adopt the Linux prototype:
> >>>> void *dev_get_drvdata(const struct device_d *dev);
> >>>>
> >>>> and do away with the error code and most of the casts.
> >>>> Users won't be able to differentiate between NULL from id table
> >>>> and NULL due to lack of drvdata, but I don't think this is
> >>>> that much of a downside, compared with not having casts obscure
> >>>> the more common pitfall (besides fec_imx.c, lm75.c, apbh_dma.c and nand_mxs.c
> >>>> are affected as well of which probably only the first is an issue.)
> >>>
> >>> Sounds good. When we change this we should rename the function
> >>> alongside, because dev_get_drvdata() does something different in Linux.
> >>
> >> Does it? I thought it does the same, with the difference that it can
> >> be set with dev_set_drvdata as well. At the cost of one extra pointer
> >> per device_d, we could have both of them.
> > 
> > dev_set_drvdata() in Linux allows you to store a pointer to private
> > driver data in struct device. We don't have a function for that in
> > barebox and use dev->priv instead.
> > dev_get_drvdata() in barebox gets you the device type data (or however
> > we want to call it). There's no function for that in Linux and we have
> > to first find out if we probe from platform data or from device tree
> > to pick the right function to get the data.
> 
> Ah, I thought the drvdata is pre-populated in Linux. I would rename
> the new function to device_get_match_data then for alignment with
> Linux, with the difference that it returns either platform data or
> device tree driver_data as appropriate.

Linux uses the of_device_get_match_data() [1] for of-based drivers.

[1] https://elixir.bootlin.com/linux/v5.8-rc4/source/drivers/of/device.c#L189

Regards,
  Marco

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