so you are using the userspace i2c_smbus_read_i2c_block_data() call from i2c-dev.h, not the kernel one from i2c-core.c, correct? Andre Fisser wrote: >>Mark Studebaker wrote: >> >>good question. >> >>you want to make the size bigger or smaller? > > > I need it to be smaller, but a maximum size of 32 is o.k. for me. > > >>I'll assume you are using a bit-banging (i2c-algo-bit) adatper here... > > > Yes. > > >>It's true, if you use the call >>i2c_smbus_read_i2c_block_data(), >>the size is fixed at 32. This is enforced in these functions >>and in i2c_smbus_xfer_emulated(). >> >>You can avoid this limitation by making a direct call to >>i2c_transfer(), you should be able to find some drivers in >>the kernel that use i2c_transfer() >>as an example. > > > I think that is too low level, I need to call that function from user-space; > I don't want to make a special driver-module for my device. > > >>If you have a proposal on a clean way to set the size on calls to >>i2c_smbus_read_i2c_block_data() >>we'll be happy to discuss it with you. > > > I have a solution that works for me. > The changes I made are quite small. I changed the > i2c_smbus_read_i2c_block_data function and added a length parameter. I think > this is the right thing to do because only the I2C master knows how many > byte to transfer. Then I pass the length in the i2c_smbus_data union in > block[0] down to all driver sub-functions, as it is done in the _write_ > functions. This allows me to adjust the block-size between 1..32, that's > good enough for me. > Of course this is a change in the API and will probably break some existing > clients. I don't have any, so no problem for me ;-) I don't know if this is > acceptable for a future version of the i2c driver. And there is still a max. > size of 32 bytes for the transfer, but changing that would require to > allocate the buffer dynamically. I think that's not worth the effort > required. > > Groetjes, > Andre > > >>Andre Fisser wrote: >> >>>Hi, >>> >>>are there plans to remove the fixed size of i2c block >> >>reads? I use the >> >>>I2C driver to communicate through the printer port with a kind of >>>Philips dongle to a custom microprocessor circuit. The fixed block >>>size is wasting bus-bandwidth which is a problem for me. >> >>I'm planning >> >>>to remove this limitation myself if there's nobody already >> >>working on >> >>>it. Maybe you guys have some advice for me how it can be best done? >>> >>>Best regards, >>>Andre >>> >>> >>>Andr? Fisser >>> >>>Imtech ICT Technical Systems >>>Flight Forum 800, >>>5657 DV Eindhoven >>> >>>Telephone +31 (0)40 8484444 >>>Fax +31 (0)40 8484440 >>>Email Andre.Fisser at Imtech.nl >>>www www.imtech.nl >>> >>>Imtech ICT is een full service ICT-dienstverlener die op een >>>no-nonsense manier bijdraagt aan het succes van haar >> >>klanten. Imtech >> >>>ICT biedt hoogwaardige dienstverlening op het gebied van >>>projectmanagement, advies, technische automatisering, >> >>informatisering >> >>>en communicatietechnologie, en is onderdeel van het beursgenoteerde >>>Imtech. >>> >>> >>> >> > >
