PCI IDE Controller: Difference between revisions

When we read a register in a channel, like STATUS Register, it is easy to execute:

 

ide_read(channel, ATA_REG_STATUS);

 

return result;

}

 

We also need a function for writing to registers:

void ide_write(unsigned char channel, unsigned char reg, unsigned char data) {

if (reg > 0x07 && reg < 0x0C)

ide_write(channel, ATA_REG_CONTROL, channels[channel].nIEN);

}

 

To read the identification space, we should read the Data Register as a double word 128 times. We can then copy them to our buffer.

 

void ide_read_buffer(unsigned char channel, unsigned char reg, unsigned int buffer,

unsigned int quads) {

ide_write(channel, ATA_REG_CONTROL, channels[channel].nIEN);

}

 

When we send a command, we should wait for 400 nanosecond, then read the Status port. If the Busy bit is on, we should read the status port again until the Busy bit is 0; then we can read the results of the command. This operation is called "Polling". We can also use IRQs instead of polling.

After many commands, if the Device Fault bit is set, there is a failure; if DRQ is not set, there is an error. If the ERR bit is set, there is an error which is described in Error port.

 

unsigned char ide_polling(unsigned char channel, unsigned int advanced_check) {

 

 

}

 

If there is an error, we have a function which prints errors on screen:

Notice that if bit 4 in HDDEVSEL is set to 1, we are selecting the slave drive, if set to 0, we are selecting the master drive.

 

// 3- Detect ATA-ATAPI Devices:

for (i = 0; i < 2; i++)

}

}

 

== Read/Write From ATA Drive ==

Lets write all these information to the register, while the obsolete bits are set (0xA0):

 

// (IV) Select Drive from the controller;

if (lba_mode == 0)

else

ide_write(channel, ATA_REG_HDDEVSEL, 0xE0 | (slavebit << 4) | head); // Drive & LBA

 

Let's write the parameters to registers:

Notice that after writing, we should execute the CACHE FLUSH command, and we should poll after it, but without checking for errors.

 

if (dma)

if (direction == 0);

return 0; // Easy, isn't it?

}

 

== Reading from an ATAPI Drive ==

Now we should select the drive:

 

// (II): Select the drive:

// ------------------------------------------------------------------

ide_write(channel, ATA_REG_HDDEVSEL, slavebit << 4);

 

400 nanoseconds delay after this select is a good idea:

 

// (III): Delay 400 nanoseconds for select to complete:

// ------------------------------------------------------------------

for(int i = 0; i < 4; i++)

ide_read(channel, ATA_REG_ALTSTATUS); // Reading the Alternate Status port wastes 100ns.

 

<syntaxhighlight lang="c">

Here we cannot poll. We should wait for an IRQ, then read the sectors. These two operations should be repeated for each sector.

 

// (IX): Receiving Data:

// ------------------------------------------------------------------

edi += (words * 2);

}

 

Now we should wait for an IRQ and poll until the Busy and DRQ bits are clear:

 

== Reading from an ATA/ATAPI Drive ==

void ide_read_sectors(unsigned char drive, unsigned char numsects, unsigned int lba,

unsigned short es, unsigned int edi) {

}

// package[0] is an entry of an array. It contains the Error Code.

 

== Writing to an ATA drive ==

 

== Ejecting an ATAPI Drive ==

void ide_atapi_eject(unsigned char drive) {

unsigned int channel = ide_devices[drive].Channel;

}

}

 

When this method is invoked, the optical device on the given channel is ejected.