Re: Aureal VOrtex update and MPU401 survey

[Takashi Iwai <tiwai@suse.de>]

Hi,

At Thu, 13 Mar 2003 00:28:39 -0400,
Manuel Jander wrote:
> 
> MPU401 survey:
> I though about a modification for the mpu401_uart driver, to allow
> a more versatil handling of different IO types. I observed that
> at least the SBLive, appart from the Vortex have a standart MPU401 port, 
> but the hardware IO is slighdely different enough to prevent the usage 
> of the existing MPU401 driver. That means the driver is copy pasted and 
> only the Register access (inb and outb) calls are modified.
> 
> Know there are too options: allow replacement functions for inb and 
> outb, or to use wrappers that accept the mpu type as parameter so that a 
> more sophisticated IO handling can be done. THat means:
> 
> case 1
> 
> typedef mpu401_t {
>    ....
>    void (*write) (u8 data, u32 addr);
>    u8 (*write) (u32 addr);
>    ....
> }
> .....
> 
> mpu->write = outb;
> mpu->read = inb;
> 
> 
> ----------- < OR >-------------------
> case 2
> 
> typedef mpu401_t {
>    ....
>    void (*write) (mpu401_t *mpu, u8 data, u32 addr);
>    u8 (*write) (mpu401_t *mpu, u32 addr);
>    ....
> }
> 
> ...
> 
> mpu->write = mpu_write;
> mpu->read = mpu_read;
> 
> 
> ... and implemented in the specific card driver:
> 
> void mpu_write(mpu401_t *mpu, u8 data, u32 addr) {
>      some_iohardware_write(mpu->private_data, data, addr);
> }
> 
> void mpu_write(mpu401_t *mpu, u8 data, u32 addr) {
>      return some_iohardware_read(mpu->private_data, addr);
> }

(i suppose the second one corresponds to read :)

i like the idea.  not only emu10k1 but some also other drivers use a
copy of mpu401_uart.c code.  for compatibility, we can keep the old
snd_mpu_uart401_new() function which works like it has been, and add a
new function with the driver-specific callbacks.

from the suggestions, i would choose the last one.  the callback
likely needs a private data to access the hardware properly.
also, for the callback argument, we don't need to pass the exact
address but only a enum CMD and DATA.


> The question is: Can anyone take advantage of having the "mpu" object 
> avaiable inside a IO wrapper ? The SBLive should, but are the 
> maintainers of the SBLive in the mood to actually make use of that ?

no problem, but unfortunately i (and perhaps Jaroslav, too) have no
time in this week to attend the LAD meeting at Karlsruhe.
so, the work will be done in the next week.


the only remaining problem is the interrupt handler.
in the case of mpu401_uart.c, there is only one interrupt handler
which handles both receive and transmit.  but some hardwares have
different rx and tx interrupts, so we need to separate them.


anyway, please feel free to submit the patch.


ciao,

Takashi


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