Hi Jeff, Thanks for your suggestions. I have done some experiment to return all ATA output register except for Read/Write command. But the aic94xx discovery machine just can not find the SATA device. Probably I will fix the new issue by next week since I have the other hot issue here. Thanks! Gilbert -----Original Message----- From: Jeff Garzik [mailto:jeff@xxxxxxxxxx] Sent: Friday, September 07, 2007 4:01 PM To: Wu, Gilbert Cc: Linux-scsi@xxxxxxxxxxxxxxx Subject: Re: [PATCH] aic94xx: fix smartctl utility problem Wu, Gilbert wrote: > HI Jeff, > > I was thinking the checking "READ/WRITE" command table is larger than > my current table. This does not cover vendor-specific command. You can implement the check in a _far_ more optimal manner: Possibility 1: static const u8 ata_rw_command_table[256] = { [ATA_CMD_READ] = 1, [ATA_CMD_READ_EXT] = 1, ... other READ/WRITE commands here, always value==1 ... }; ... u8 ata_command = ... ; if (ata_rw_command_table[ata_command]) { /* it is a read/write command */ } else { /* it is NOT a read/write command */ } Possibility 2: static inline int is_ata_rw_cmd(u8 ata_cmd) { switch (ata_cmd) { case ATA_CMD_READ: case ATA_CMD_READ_EXT: ... other READ/WRITE commands here ... return 1; } return 0; } Either way you avoid the iteration, and simplify things down to a single test. Once that is done, it should be self-evident that testing -any- list of commands is O(1), rather than O(n) for the case of table iteration. And therefore, the cost of checking "is it a READ/WRITE command?" is equal to the cost of checking for any other commands. > Do you wan me just check READ/WRITE command? Yes, please. > The aic94xx default implementation is all ATA command will be returning > ATA output register if the command did not succeed. Great! Jeff - To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
