João Ramos escreveu:
Yes! :)
There is still a room for improvement though -- it would be better to
fix
IDE core to set PIO0 before probing devices for all host controllers.
Moreover it seems that doing it this way would allow us to remove
->init_hwif
method from this driver and do all necessary setup in ep93xx_ide_probe()
(this controller is a single port one so theoretically there
shouldn't be
a need for having per-port ->init_hwif implementation).
So after all this discussion ;-) , my driver will have no 'init_hwif'
method, and the setup code will be on 'ep93xx_ide_probe', which will
configure entirely the IDE host controller.
Moreover, this initial configuration will setup the controller to work
at PIO Mode 0. Later on, the 'set_pio_mode' method will be called and
the controller will configure itself according to the PIO mode
reported by the IDE core.
Can I proceed this way?
There's just only one issue; normally, I would setup the specific
timings (t0, t1, t2, t2i, etc) in the 'pio_set_mode' hook. However,
if you look further in the driver, those timings aren't defined
through a memory controller but instead manually enforced by
'ndelay' calls (arghhh).
This means that in my low-level procedures for reading and writing,
I need to have access to the timings (or the struct ide_timing)
corresponding to the PIO mode selected, in order to use the correct
delays.
My question is: which is the best way to accomplish this? Declaring
a global struct ide_timing variable pointer that always holds the
correct ide_timing struct to the selected PIO mode? Or should I
always check (in some manner) what is the current PIO mode and then
select the adequate delays?
I think that the setting variable pointer in ->set_pio_mode method would
work best. Seems like the existing drive_data field of ide_drive_t
is well
suited for this purpose (however it may be worth to convert it to
'void *'
type while we are it).
Are you sure I can do this safely?
Using the patch i've sent earlier, I am using the 'drive_data' field
(now converted to void * type) to store the struct ide_timing pointer
that holds the adequate timings for the selected PIO mode.
This is working, and the fix you suggested works, but sometimes I get a
null pointer dereference I can't seem to figure why.
As I needed to define low-level read/write procedures, I've defined the
entire ide_tp_ops structure with my own provided methods.
For the tf_load, tf_read, input_data and output_data methods, the fix is
easy since I have an ide_drive_t structure pointer as a parameter, so I
access the timing structure using:
struct ide_timing *t = (struct ide_timing *) ide_get_drivedata(drive);
However, for the remaining methods (exec_command, read_status,
read_altstatus, write_devctl and dev_select), I only have access to an
ide_hwif_t pointer, so in order to get access to the containing
ide_drive_t and then to the struct ide_timing pointer stored before, I do:
ide_drive_t *drive = (ide_drive_t *) container_of(&hwif, ide_drive_t, hwif);
struct ide_timing *t = (struct ide_timing *) ide_get_drivedata(drive);
And this seems to work, however at some point, after a while I get a
kernel Oops pointing out a null pointer dereference.
Can someone help me here?
Is there a better way to retrieve the ide_drive_t pointer from the
ide_hwif_t structure?
Best regards,
João Ramos
--
************************************************************************
João Ramos <joao.ramos@xxxxxxx>
INOV INESC Inovação - ESTG Leiria
Escola Superior de Tecnologia e Gestão de Leiria
Edíficio C1, Campus 2
Morro do Lena, Alto do Vieiro
Leiria
2411-901 Leiria
Portugal
Tel: +351244843424
Fax: +351244843424
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