On Monday 01 December 2008, Hiremath, Vaibhav wrote:
> >
> > Another common use of driver_data is to hold a pointer
> > to a struct holding chip-specific data that doesn't fit
> > into a simple bitmask.
> >
> [Hiremath, Vaibhav] I am trying to use/save complete init sequence in
> id->driver_data -
>
> static const struct i2c_device_id tvp514x_id[] = {
> {"tvp5146", (unsigned int)&tvp5146_init},
Well, kernel_ulong_t ...
> {"tvp5146m2", (unsigned int)&tvp514xm_init},
> {"tvp5147", (unsigned int)&tvp5147_init},
> {"tvp5147m1", (unsigned int)&tvp514xm_init},
> {},
> };
>
> NOTE: Please note that init sequence for 46, 47 are different.
>
> But I came to know that, client structure doesn't have any parameter
> which will provide me the index under this id table. The only
> differentiating parameter we have is "name" (decoder->client->driver->name).
Right; why would you need an index, if you've got the pointer you
were going to use to look it up anyway?
struct tvp_init {
enum tvp_id id; /* tvp5146, tvp5146m2, etc */
short *entries; /* ((addr << 8) | value, etc */
unsigned n_entries;
};
struct tvp_init tvp515xm_init = { ... };
... etc
> I can use "id->driver_data" only in my probe function without any index.
>
> So left with only following options -
>
> 1)
> if (strcmp(id->name, "tvp5146") == 0)
> /* original 46 init seq */;
> else if (strcmp(id->name, "tvp5147") == 0)
> /* original 47 init seq */
> else if ((strmcp(id->name, "tvp5146m2") == 0) ||
> (strmcp(id->name, "tvp5147m1") == 0))
> /* New 46/47 init seq */
Avoid that; it's already been done before you, if you pass the
right info in driver_data.
> 2)
>
> Driver specific structure must contain either of
By "driver specific structure" do you mean what the
board init code stores in i2c_client.dev.platform_data?
I'm assuming that's what you mean ... but of course, a
second driver-specific structure is what you'd normally
store in probe() and retrieve with i2c_get_clientdata().
> - Index of i2c_device_id table, use this to get the driver_data.
> (This also requires string compare to get the index.)
No, you're given the i2c_device_id entry as a probe() parameter.
Just dereference id to get driver_data; no stable index numbers
needed. Store it away along through i2c_get_clientdata() if
you need it later.
> - Pointer to init_reg_seq, which is pointer to array of structure
> for tvp514x_regs. This is little bit ugly, since will have to
> export tvp514x_regs structure.
The platform_data should not hold such stuff; it's not board-specific.
I'd expect platform_data to hold regulator_init_data as needed to
instantiate the regulator; and maybe other stuff needed on this board
too. Floor and ceiling parameters, maybe, unless they change at runtime.
The init sequence wouldn't matter at all for i2c_get_clientdata(),
since it should only kick in during probe().
> - Or have pointer to i2c_device_id itself. (Implemented and tested)
Hmm, now I'm not sure what you mean. Were you talking about
the i2c_get_clientdata() stuff instead?
> I prefer to use second option, instead of comparing the name string in
> s_power every time. And it will be very easy to add even more chips
> providing generic solution; we need to just add entry to i2c_device_id
> with expected init sequence and you are done.
If I interpret your words correctly, I agree. The whole point of
the id table is to let probe just use the "id" directly to get at
descriptors with chip-specific data.
- Dave
> Any suggestions or inputs appreciated???
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