Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757197Ab1CIPKk (ORCPT ); Wed, 9 Mar 2011 10:10:40 -0500 Received: from iolanthe.rowland.org ([192.131.102.54]:57183 "HELO iolanthe.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1757072Ab1CIPKh (ORCPT ); Wed, 9 Mar 2011 10:10:37 -0500 Date: Wed, 9 Mar 2011 10:10:36 -0500 (EST) From: Alan Stern X-X-Sender: stern@iolanthe.rowland.org To: Roger Quadros cc: gregkh@suse.de, , Subject: Re: [PATCH 1/3] usb: gadget: storage: Add fsg_get_toc helper In-Reply-To: <1299673300-16726-2-git-send-email-roger.quadros@nokia.com> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3741 Lines: 109 On Wed, 9 Mar 2011, Roger Quadros wrote: > fsg_get_toc can be used by both storage gadgets to build a CD-ROM > Table of Contents which can be used as data for READ_TOC command. > Currently fsg_get_toc supports two TOC formats, i.e. > format 0: Formatted TOC and format 2: Raw TOC. > > Raw TOC is required for CD-ROM emulation to work with Mac OS-X. In addition to the things Sergei mentioned... > +/* > + * put_toc() - Builds a TOC with required format @format. > + * @curlun: The LUN for which the TOC has to be built > + * @msf: Min Sec Frame format or LBA format for address > + * @format: TOC format code > + * @buf: the buffer into which the TOC is built > + * > + * Builds a Table of Content which can be used as data for READ_TOC command. > + * The TOC simulates a single session, single track CD-ROM mode 1 disc. > + * > + * Returns number of bytes written to @buf, -EINVAL if format not supported. > + */ > +static int fsg_get_toc(struct fsg_lun *curlun, int msf, int format, u8 *buf) > +{ > + switch (format) { > + case 0: > + /* Formatted TOC */ > + memset(buf, 0, 20); > + buf[1] = (20-2); /* TOC data length */ > + buf[2] = 1; /* First track number */ > + buf[3] = 1; /* Last track number */ > + buf[5] = 0x16; /* Data track, copying allowed */ > + buf[6] = 0x01; /* Only track is number 1 */ > + store_cdrom_address(&buf[8], msf, 0); > + > + buf[13] = 0x16; /* Lead-out track is data */ > + buf[14] = 0xAA; /* Lead-out track number */ > + store_cdrom_address(&buf[16], msf, curlun->num_sectors); > + return 20; > + break; > + > + case 2: > + /* Raw TOC */ > + memset(buf, 0, 37); /* Header + A0, A1 & A2 descriptors */ > + buf[1] = 37; /* 4 + 3*11 */ There's no reason to do it this way. The compiler is a lot better than you are at addition. Just put 4 + 3*11 in the assignment statement, and in the comment explain what the numbers mean. > + buf[2] = 1; /* First complete session */ > + buf[3] = 2; /* Last complete session */ > + > + buf += 4; > + /* A0 point */ > + buf[0] = 1; /* Session number */ > + buf[1] = 0x16; /* Data track, copying alowed */ > + /* 2 - Track number 0 -> TOC */ > + buf[3] = 0xA0; /* Point A0 */ > + /* 4, 5, 6 - Min, sec, frame is zero */ > + /* 7 - zero */ > + buf[8] = 1; /* Pmin: 1st track number */ > + /* 9 - disc type 0: CD-ROM/DA with 1st track in mode 1 */ > + /* 10 - pframe 0 */ > + > + buf += 11; > + /* A1 point*/ > + buf[0] = 1; /* Session number */ > + buf[1] = 0x16; /* Data track, copying alowed */ > + /* 2 - Track number 0 -> TOC */ > + buf[3] = 0xA1; /* Point A1 */ > + /* 4, 5, 6 - Min, sec, frame is zero */ > + /* 7, zero */ > + buf[8] = 1; /* Pmin: last track number */ > + /* 9, 10 - pmin and pframe are 0 */ > + > + buf += 11; > + /* A2 point*/ > + buf[0] = 1; /* Session number */ > + buf[1] = 0x16; /* Data track, copying alowed */ > + /* 2 - Track number 0 -> TOC */ > + buf[3] = 0xA2; /* Point A2 */ > + /* 4, 5, 6 - Min, sec, frame is zero */ > + /* 7, 8, 9, 10 - zero, Pmin, Psec, Pframe of Lead out */ > + store_cdrom_address(&buf[7], msf, curlun->num_sectors); These things could be put into a loop, instead of a separate function. > + return 37; It might be a good idea to use a variable instead of having all these "37"s floating around. It would make future updates more reliable. > + break; > + default: > + /* Multi-session, PMA, ATIP, CD-TEXT not supported/required */ > + return -EINVAL; > + break; > + } > +} Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/