On Wednesday 18. August 2010 18.27.16 Ameya Palande wrote: > Hi Thiago, > > On Wed, 2010-08-18 at 18:16 +0200, ext Thiago Macieira wrote: > > On Wednesday 18 August 2010 15:09:37 Arjan van de Ven wrote: > > > On 8/18/2010 3:19 AM, Carsten Munk wrote: > > > > [this is not another SSSE3 discussion thread] > > > > > > > > Qt on OMAP3 has very big benefits from using NEON, just like using > > > > SSSE3 does on Atom. However, we do not currently compile for NEON in > > > > MeeGo for ARMv7 as not all ARMv7 has NEON (Marvell, Nvidia being > > > > notable exceptions). > > > > > > > > We'd obviously like to use NEON on Nokia N900 but we're wondering how > > > > to do this in the most ecosystem-friendly way. > > > > > > > > I have been talking to Thiago and he mentions that an environment > > > > variable QT_NO_NEON=1 exists to disable NEON usage by Qt. > > > > > > > > So, my proposal is the following: > > > > > > > > Compile Qt with NEON support by default on ARMv7. Include script in > > > > startup that provides QT_NO_NEON=1 to the UX session based on NEON > > > > presence in /proc/cpuinfo. > > > > > > couldn't QT read /proc/cpuinfo (or do the equivalent of cpuid) instead > > > of looking for the env variable? > > > > I don't know how the kernel detects the presence of the Neon coprocessor. > > But looking at ARM documentation doesn't show any instruction for cpuid. > > In general, for embedded devices, you don't need cpuid since "you know > > what you put in your device". > > > > The kernel also passes the CPU capabilities to the process in the auxv, > > but that is not exposed anywhere outside ld.so. > > How about "/proc/self/auxv"?
Thanks, that's a good hint. That is binary format and thus easier to parse. My
N900 shows 0x30d3 as features. If I read the kernel source right
(asm/hwcap.h), this translates to:
swp half fastmult vfp edsp neon vfpv3
--
Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org
Senior Product Manager - Nokia, Qt Development Frameworks
PGP/GPG: 0x6EF45358; fingerprint:
E067 918B B660 DBD1 105C 966C 33F5 F005 6EF4 5358
signature.asc
Description: This is a digitally signed message part.
_______________________________________________ MeeGo-dev mailing list [email protected] http://lists.meego.com/listinfo/meego-dev
