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
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