linux-kernel - Re: [PATCH v2 1/3] spi: add xtfpga SPI controller driver

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Wed, 12 Mar 2014 21:13:35 +0400
From:	Max Filippov <jcmvbkbc@...il.com>
To:	Mark Brown <broonie@...nel.org>
Cc:	"linux-xtensa@...ux-xtensa.org" <linux-xtensa@...ux-xtensa.org>,
	linux-spi@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Chris Zankel <chris@...kel.net>,
	Marc Gauthier <marc@...ence.com>,
	Rob Herring <robh+dt@...nel.org>,
	Grant Likely <grant.likely@...aro.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v2 1/3] spi: add xtfpga SPI controller driver

On Wed, Mar 12, 2014 at 4:49 PM, Mark Brown <broonie@...nel.org> wrote:
> On Wed, Mar 12, 2014 at 04:21:03PM +0400, Max Filippov wrote:
>
>> +     case 16:
>> +             /* Bytes that should go out earlier have lower addresses,
>> +              * but the hardware operates with 16 bit words and transmits
>> +              * higher bits first. Thus data in memory is in BE order.
>> +              */
>> +             xspi->data = (xspi->data << 16) | be16_to_cpu(v);
>> +             xspi->data_sz += 2;
>> +             break;
>
> Are you sure you need to do this byte swap?  SPI words are big endian so
> if you are running on a little endian processor if you are transmitting
> 16 bit words you should see the data getting swapped on the bus (this is
> why I say you should never have more than 8 bits per word for regmap).

Looks like this swap is not needed: I've looked at drivers that set
bits_per_word = 16, they submit data in cpu endianness. Will fix in v3.

-- 
Thanks.
-- Max
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/