Date: Thu, 28 Aug 2003 23:25:10 +0200 (CEST) From: Mikulas Patocka <mikulas@artax.karlin.mff.cuni.cz> To: Dan Lukes <dan@obluda.cz> Cc: freebsd-hackers@freebsd.org Subject: Re: Bug FreeBSD 4.8 ATA driver Message-ID: <Pine.LNX.4.44.0308271545120.22196-100000@artax.karlin.mff.cuni.cz> In-Reply-To: <3F4B5374.1080306@obluda.cz>
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On Tue, 26 Aug 2003, Dan Lukes wrote: > Mikulas Patocka napsal/wrote, On 08/20/03 01:39: > > I am reading FreeBSD ATA drivers because I want to use them as base for my > > ATA driver and I found a total nonsence: in ata-dma.c in FreeBSD 4.8, > > there is line > > > > if (!((pci_read_config(parent,0x40,4)>>(ch->unit<<8))&0x4000)) { > > > > if ch->unit is 1, config word is shifted by 256 bytes, which gives > > undefined result in C. How was this meant? What should it do? > > Hm, it should be (IMHO) > if (!((pci_read_config(parent,0x40,4)>>(ch->unit<<5))&0x4000)) That is incorrect too --- if ch->unit is 1, ch->unit<<5 is 32 and you can't shift 32-bit integer by 32 bits. > but I can't verify it as have no access to documentation for PIIX3 nor > acces to the PIIX3 hardware now. > > Note the position of '8' just above the '5' key on numeric keypad also ... > > FYI, the gcc compile the code as equivalent of > if (!((pci_read_config(parent,0x40,4)>>(0))&0x4000)) > effectively ignoring the ch->unit number. > > > If you want wrote your own ATA driver, it may be better to look into > current FreeBSD 5 ATA code - it's substantially rewrited. I noticed it too late --- when I copid all code from FreeBSD 4 :-/ > A smel bych, uz asi mimo konferenci, vedet, proc si pises vlastni ATA > ovladac ? No, zatim to neni moc verejny projekt. Mikulas
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