From mboxrd@z Thu Jan 1 00:00:00 1970 From: Albert Lee Subject: Re: [PATCH 2/6] libata: add xfer_mask handling functions Date: Tue, 07 Mar 2006 13:51:05 +0800 Message-ID: <440D1F49.5040508@tw.ibm.com> References: <11415871161635-git-send-email-htejun@gmail.com> Reply-To: albertl@mail.com Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from e33.co.us.ibm.com ([32.97.110.151]:55494 "EHLO e33.co.us.ibm.com") by vger.kernel.org with ESMTP id S1750861AbWCGFvP (ORCPT ); Tue, 7 Mar 2006 00:51:15 -0500 Received: from westrelay02.boulder.ibm.com (westrelay02.boulder.ibm.com [9.17.195.11]) by e33.co.us.ibm.com (8.12.11/8.12.11) with ESMTP id k275p9AO016599 for ; Tue, 7 Mar 2006 00:51:09 -0500 Received: from d03av03.boulder.ibm.com (d03av03.boulder.ibm.com [9.17.195.169]) by westrelay02.boulder.ibm.com (8.12.10/NCO/VER6.8) with ESMTP id k275mSTY261944 for ; Mon, 6 Mar 2006 22:48:28 -0700 Received: from d03av03.boulder.ibm.com (loopback [127.0.0.1]) by d03av03.boulder.ibm.com (8.12.11/8.13.3) with ESMTP id k275p8TD005144 for ; Mon, 6 Mar 2006 22:51:09 -0700 In-Reply-To: <11415871161635-git-send-email-htejun@gmail.com> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Tejun Heo Cc: jgarzik@pobox.com, alan@lxorguk.ukuu.org.uk, linux-ide@vger.kernel.org Tejun Heo wrote: > Add ata_pack_xfermask(), ata_xfer_mask2mode(), ata_xfer_mode2mask(), > ata_xfer_mode2shift() and ata_id_xfermask(). These functions will be > used by following patches to simplify xfer_mask handling. > > Signed-off-by: Tejun Heo > > (snip) > +/** > + * ata_id_xfermask - Compute xfermask from the given IDENTIFY data > + * @id: IDENTIFY data to compute xfer mask from > + * > + * Compute the xfermask for this device. This is not as trivial > + * as it seems if we must consider early devices correctly. > + * > + * FIXME: pre IDE drive timing (do we care ?). > + * > + * LOCKING: > + * None. > + * > + * RETURNS: > + * Computed xfermask > + */ > +static unsigned int ata_id_xfermask(const u16 *id) > +{ > + unsigned int pio_mask, mwdma_mask, udma_mask; > + > + /* Usual case. Word 53 indicates word 64 is valid */ > + if (id[ATA_ID_FIELD_VALID] & (1 << 1)) { > + pio_mask = id[ATA_ID_PIO_MODES] & 0x03; > + pio_mask <<= 3; > + pio_mask |= 0x7; > + } else { > + /* If word 64 isn't valid then Word 51 high byte holds > + * the PIO timing number for the maximum. Turn it into > + * a mask. > + */ > + pio_mask = (2 << (id[ATA_ID_OLD_PIO_MODES] & 0xFF)) - 1 ; > + > + /* But wait.. there's more. Design your standards by > + * committee and you too can get a free iordy field to > + * process. However its the speeds not the modes that > + * are supported... Note drivers using the timing API > + * will get this right anyway > + */ > + } > + > + mwdma_mask = id[ATA_ID_MWDMA_MODES] & 0x07; > + udma_mask = id[ATA_ID_UDMA_MODES] & 0xff; > + > + return ata_pack_xfermask(pio_mask, mwdma_mask, udma_mask); > +} > + > /* We have ap->pio_mask, ap->mwdma_mask and ap->udma_mask. Just thinking what if we have these masks in ata_device? Maybe we can save some bitwise operations and make the code more intuitive to read? Ex. ata_id_xfermask() can store the calculated masks to dev->pio_mask, dev->mwdma_mask, etc. Ex. ata_mode_string() can take mode (XFER_UDMA_7..) as parameter and translate the given mode to string. Ex. to print out the max mode support by the device, 1. ata_id_xfermask() calculates and saves the masks to dev->pio_mask, etc. 2. Another function, say, ata_dev_max_mode() takes dev as parameter, packs the mode by ata_pack_xfermask() internally, find the max mode supported by the drive, then use ata_xfer_mask2mode() to return the mode. 3. ata_mode_string() translates the mode, say XFER_UDMA_7, to string literal. Albert