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MCA Driver Programming Interface

Introduction

The MCA bus functions provide a generalised interface to find MCA bus cards, to claim them for a driver, and to read and manipulate POS registers without being aware of the motherboard internals or certain deep magic specific to onboard devices.

The basic interface to the MCA bus devices is the slot. Each slot is numbered and virtual slot numbers are assigned to the internal devices. Using a pci_dev as other busses do does not really make sense in the MCA context as the MCA bus resources require card specific interpretation.

Finally the MCA bus functions provide a parallel set of DMA functions mimicing the ISA bus DMA functions as closely as possible, although also supporting the additional DMA functionality on the MCA bus controllers.

Known Bugs And Assumptions

None.

Public Functions Provided

  • mca_find_adapter - scan for adapters

Synopsis:

int mca_find_adapter ( int id )

Arguments:

  • id - MCA identification to search for
  • start - starting slot

Description:

Search the MCA configuration for adapters matching the 16bit ID given. The first time it should be called with start as zero and then further calls made passing the return value of the previous call until MCA_NOTFOUND is returned.

Disabled adapters are not reported.

  • mca_find_unused_adapter - scan for unused adapters

Synopsis:

int mca_find_unused_adapter ( int id )

Arguments:

  • id - MCA identification to search for
  • start - starting slot

Description:

Search the MCA configuration for adapters matching the 16bit ID given. The first time it should be called with start as zero and then further calls made passing the return value of the previous call until MCA_NOTFOUND is returned.

Adapters that have been claimed by drivers and those that are disabled are not reported. This function thus allows a driver to scan for further cards when some may already be driven.

  • mca_read_stored_pos - read POS register from boot data

Synopsis:

unsigned char mca_read_stored_pos ( int slot )

Arguments:

  • slot - slot number to read from
  • reg - register to read from

Description:

Fetch a POS value that was stored at boot time by the kernel when it scanned the MCA space. The register value is returned. Missing or invalid registers report 0.

  • mca_read_pos - read POS register from card

Synopsis:

unsigned char mca_read_pos ( int slot )

Arguments:

  • slot - slot number to read from
  • reg - register to read from

Description:

Fetch a POS value directly from the hardware to obtain the current value. This is much slower than mca_read_stored_pos and may not be invoked from interrupt context. It handles the deep magic required for onboard devices transparently.

  • mca_write_pos - read POS register from card

Synopsis:

void mca_write_pos ( int slot )

Arguments:

  • slot - slot number to read from
  • reg - register to read from
  • byte - byte to write to the POS registers

Description:

Store a POS value directly from the hardware. You should not normally need to use this function and should have a very good knowledge of MCA bus before you do so. Doing this wrongly can damage the hardware.

This function may not be used from interrupt context.

Note that this a technically a Bad Thing, as IBM tech stuff says you should only set POS values through their utilities. However, some devices such as the 3c523 recommend that you write back some data to make sure the configuration is consistent. I'd say that IBM is right, but I like my drivers to work.

This function can't do checks to see if multiple devices end up with the same resources, so you might see magic smoke if someone screws up.

  • mca_set_adapter_name - Set the description of the card

Synopsis:

void mca_set_adapter_name ( int slot )

Arguments:

  • slot - slot to name
  • name - text string for the namen

Description:

This function sets the name reported via /proc for this adapter slot. This is for user information only. Setting a name deletes any previous name.

  • mca_mark_as_used - claim an MCA device

Synopsis:

int mca_mark_as_used ( int slot )

Arguments:

  • slot - slot to claim

FIXME:

should we make this threadsafe

Claim an MCA slot for a device driver. If the slot is already taken the function returns 1, if it is not taken it is claimed and 0 is returned.

  • mca_mark_as_unused - release an MCA device

Synopsis:

void mca_mark_as_unused ( int slot )

Arguments:

  • slot - slot to claim

Description:

Release the slot for other drives to use.

DMA Functions Provided

  • mca_enable_dma - channel to enable DMA on

Synopsis:

void mca_enable_dma ( unsigned int dmanr )

Arguments:

  • dmanr - DMA channel

Description:

Enable the MCA bus DMA on a channel. This can be called from IRQ context.

  • mca_disable_dma - channel to disable DMA on

Synopsis:

void mca_disable_dma ( unsigned int dmanr )

Arguments:

  • dmanr - DMA channel

Description:

Enable the MCA bus DMA on a channel. This can be called from IRQ context.

  • mca_set_dma_addr - load a 24bit DMA address

Synopsis:

void mca_set_dma_addr ( unsigned int dmanr )

Arguments:

  • dmanr - DMA channel
  • a - 24bit bus address

Description:

Load the address register in the DMA controller. This has a 24bit limitation (16Mb).

  • mca_get_dma_addr - load a 24bit DMA address

Synopsis:

unsigned int mca_get_dma_addr ( unsigned int dmanr )

Arguments:

  • dmanr - DMA channel

Description:

Read the address register in the DMA controller. This has a 24bit limitation (16Mb). The return is a bus address.

  • mca_set_dma_count - load a 16bit transfer count

Synopsis:

void mca_set_dma_count ( unsigned int dmanr )

Arguments:

  • dmanr - DMA channel
  • count - count

Description:

Set the DMA count for this channel. This can be up to 64Kbytes. Setting a count of zero will not do what you expect.

  • mca_get_dma_residue - get the remaining bytes to transfer

Synopsis:

unsigned int mca_get_dma_residue ( unsigned int dmanr )

Arguments:

  • dmanr - DMA channel

Description:

This function returns the number of bytes left to transfer on this DMA channel.

  • mca_set_dma_io - set the port for an I/O transfer

Synopsis:

void mca_set_dma_io ( unsigned int dmanr )

Arguments:

  • dmanr - DMA channel
  • io_addr - an I/O port number

Description:

Unlike the ISA bus DMA controllers the DMA on MCA bus can transfer with an I/O port target.

  • mca_set_dma_mode - set the DMA mode

Synopsis:

void mca_set_dma_mode ( unsigned int dmanr )

Arguments:

  • dmanr - DMA channel
  • mode - mode to set

Description:

The DMA controller supports several modes. The mode values you can set are-

MCA_DMA_MODE_READ when reading from the DMA device.

MCA_DMA_MODE_WRITE to writing to the DMA device.

MCA_DMA_MODE_IO to do DMA to or from an I/O port.

MCA_DMA_MODE_16 to do 16bit transfers.

About This Book

Authors

  • Alan Cox
  • David Weinehall
  • Chris Beauregard

Copyright 2000

  • Alan Cox
  • David Weinehall
  • Chris Beauregard

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