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Date:   Fri, 12 Jun 2020 09:33:45 +0200
From:   Miquel Raynal <miquel.raynal@bootlin.com>
To:     =?UTF-8?B?w4FsdmFybyBGZXJuw6FuZGV6?= Rojas <noltari@gmail.com>
Cc:     Florian Fainelli <f.fainelli@gmail.com>, tsbogend@alpha.franken.de,
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        vigneshr@ti.com, Jonas Gorski <jonas.gorski@gmail.com>,
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        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-mtd@lists.infradead.org
Subject: Re: [PATCH v2] mtd: parsers: bcm63xx: simplify CFE detection
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Hi Álvaro,

Álvaro Fernández Rojas <noltari@gmail.com> wrote on Fri, 12 Jun 2020
09:30:27 +0200:

> Hi Miquèl,
> 
> > El 12 jun 2020, a las 9:02, Miquel Raynal <miquel.raynal@bootlin.com> escribió:
> > 
> > Hi Álvaro,
> > 
> > Álvaro Fernández Rojas <noltari@gmail.com> wrote on Thu, 11 Jun 2020
> > 18:14:20 +0200:
> >   
> >> Hi Florian,
> >>   
> >>> El 11 jun 2020, a las 17:42, Florian Fainelli <f.fainelli@gmail.com> escribió:
> >>> 
> >>> 
> >>> 
> >>> On 6/11/2020 8:16 AM, Álvaro Fernández Rojas wrote:    
> >>>> Hi Miquel,
> >>>>   
> >>>>> El 11 jun 2020, a las 9:55, Miquel Raynal <miquel.raynal@bootlin.com> escribió:
> >>>>> 
> >>>>> Hi Álvaro,
> >>>>> 
> >>>>> Álvaro Fernández Rojas <noltari@gmail.com> wrote on Mon,  8 Jun 2020
> >>>>> 18:06:49 +0200:
> >>>>>   
> >>>>>> Instead of trying to parse CFE version string, which is customized by some
> >>>>>> vendors, let's just check that "CFE1" was passed on argument 3.
> >>>>>> 
> >>>>>> Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>
> >>>>>> Signed-off-by: Jonas Gorski <jonas.gorski@gmail.com>
> >>>>>> ---
> >>>>>> v2: use CFE_EPTSEAL definition and avoid using an additional funtion.
> >>>>>> 
> >>>>>> drivers/mtd/parsers/bcm63xxpart.c | 29 ++++-------------------------
> >>>>>> 1 file changed, 4 insertions(+), 25 deletions(-)
> >>>>>> 
> >>>>>> diff --git a/drivers/mtd/parsers/bcm63xxpart.c b/drivers/mtd/parsers/bcm63xxpart.c
> >>>>>> index 78f90c6c18fd..493a75b2f266 100644
> >>>>>> --- a/drivers/mtd/parsers/bcm63xxpart.c
> >>>>>> +++ b/drivers/mtd/parsers/bcm63xxpart.c
> >>>>>> @@ -22,6 +22,9 @@
> >>>>>> #include <linux/mtd/partitions.h>
> >>>>>> #include <linux/of.h>
> >>>>>> 
> >>>>>> +#include <asm/bootinfo.h>
> >>>>>> +#include <asm/fw/cfe/cfe_api.h>    
> >>>>> 
> >>>>> Are you sure both includes are needed?    
> >>>> 
> >>>> asm/bootinfo.h is needed for fw_arg3 and asm/fw/cfe/cfe_api.h is needed for CFE_EPTSEAL.
> >>>>   
> >>>>> 
> >>>>> I don't think it is a good habit to include asm/ headers, are you sure
> >>>>> there is not another header doing it just fine?    
> >>>> 
> >>>> Both are needed unless you want to add another definition of CFE_EPTSEAL value.
> >>>> There are currently two CFE magic definitions, the one in asm/fw/cfe/cfe_api.h and another one in bcm47xxpart.c:
> >>>> https://github.com/torvalds/linux/blob/master/arch/mips/include/asm/fw/cfe/cfe_api.h#L28
> >>>> https://github.com/torvalds/linux/blob/master/drivers/mtd/parsers/bcm47xxpart.c#L33    
> >>> 
> >>> The caveat with that approach is that this reduces the compilation
> >>> surface to MIPS and BMIPS_GENERIC and BCM63XX only, which is a bit
> >>> small. If we could move the CFE definitions to a shared header, and
> >>> consolidate the value used by bcm47xxpart.c as well, that would allow us
> >>> to build the bcm63xxpart.c file with COMPILE_TEST on other
> >>> architectures. This does not really have functional value, but for
> >>> maintainers like Miquel, it allows them to quickly test their entire
> >>> drivers/mtd/ directory.    
> >> 
> >> I don’t think fw_arg3 available on non mips archs, is it?
> >> I’m happy to move it to a shared header (which would be a good location for this?), but if I’m right it would still be restricted to MIPS.  
> > 
> > Restricting a definition to MIPS, even if it makes sense for you is
> > very limiting for me. I need to be able to build as much drivers as I
> > can from my laptop and verify they at least compile correctly. If I need
> > a MIPS toolchain, an ARC toolchain, a PowerPC, an ARM, an ARM64 and
> > whatever other funky toolchain to do just that in X steps: it's very
> > painful. We have been adding COMPILE_TEST dependencies on as much
> > drivers as we could and we want to continue moving forward. Using such
> > include would need to drop the COMPILE_TEST condition from Kconfig and
> > this is not something I am willing to do.  
> 
> I totally understand and agree with your point, but I still think that there could be a solution which would be valid for both of us.

What do you suggest?

> 
> > 
> > Thanks for your understanding :)  
> 
> The current way of detecting CFE isn’t the proper one.
> Thank you for understanding that too.

Of course, I'm not saying I don't want this change, I'm just saying we
should find another way to handle it, the below idea is totally fine by
me.


Thanks,
Miquèl