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    SubjectPreferred kernel API/ABI for accelerator hardware device driver

    I am looking for advice on the proper design of an API for a device driver
    for hardware acceleration (e.g. a JPEG decoder or a cryptographic function
    accelerator). These hardware modules don’t appear to map properly to the
    standard device-driver paradigm (i.e., a “device file” that communicates
    with userspace using read()/write() system calls), as we need to pass input
    data into the kernel and receive transformed output directly. The only way I
    see to use standard IO operations on such drivers is by copying the data
    into temporary kernel buffers, which is (a) a pain and (b) horribly

    Currently the only way I see around this limitation is to implement all
    communications with such a driver using ioctl() operations, but this isn’t a
    very satisfactory solution—for example, it does not provide a way to do
    something similar to “writev()” (gathering several buffers for a single
    processing operation).

    Should I just take the plunge and implement a new “iov(fd, iov_in,
    iovcnt_in, iov_out, iovcnt_out)” system call?
    Does anyone have a better idea for an interface that will allow zero-copy
    interfacing to a transformation driver from userspace?


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      Last update: 2009-05-31 13:17    [W:0.036 / U:5.716 seconds]
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