> James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>: > > On Tue, 2015-02-10 at 10:30 -0500, John David Anglin wrote: >> On 2015-02-10 5:31 AM, Held Bier wrote: >>> Hi. >>> >>> Looks like PA-RISC 1.1 added bi-endian support. >>> What about PA-RISC Linux? I know it's big endian. >>> But does it possible to build little endian kernel? If so, how? >>> Is migration to little endian planned? It should be reasonable >>> as it will bring more compatibility with other Linux world. > > What compatibility? x86 is LE, Arm is Schizophrenic, PPC, Sparc and PA > are BE. We're required to support the bus standards anyway, so the SCSI > bus is BE and the PCI bus LE by spec. There's no such thing as a > "compatible" endianness. Some software authors still assume that we're living in x86 only world, or just don't care. This leads to issues when one wish to run such software on a BE Linux. POWER is moving to LE: https://www.ibm.com/developerworks/community/blogs/fe313521-2e95-46f2-817d-44a4f27eba32/entry/just_the_faqs_about_little_endian "Although Power already has Linux distributions and supporting applications that run in big endian mode, the Linux application ecosystem for x86 platforms is much larger and Linux on x86 uses little endian mode. Numerous clients, software partners, and IBM’s own software developers have told us that porting their software to Power becomes simpler if the Linux environment on Power supports little endian mode, more closely matching the environment provided by Linux on x86. This new level of support will lower the barrier to entry for porting Linux on x86 software to Linux on Power." For PPC the patch was made: http://lwn.net/Articles/408845/ > >> Unlikely. According to the PA 2.0 arch, implementation of this feature >> was optional. > > I think it was originally designed for some type of LASI system. > There's an endian flip in some of the LASI devices as well. I think the > original problem was LASI was designed big endian, but the chosen SCSI > processor was designed for LE at that time, so they tried to flip the > processor. I suspect the reason the feature became optional is that it > caused more problems than it solved. > >> Further the PDC/IODC firmware and software tool chains need little >> endian support. This >> is a massive amount of work. So, unless one one decided to create a >> 64-bit embedded >> PA-RISC processor for mass deployment, it wouldn't be worth the effort. > > It's a bit pointless too. Coping with endianness isn't really an > unsolved OS problem, so it would cost a huge amount, open a large can of > worms and buy us nothing. > > James > > -- To unsubscribe from this list: send the line "unsubscribe linux-parisc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
