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    SubjectRe: [PATCH 1/2] PRUSS UIO driver support
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    On Friday 18 February 2011, Pratheesh Gangadhar wrote:
    > Signed-off-by: Pratheesh Gangadhar <pratheesh@ti.com>
    >
    > This patch implements PRUSS (Programmable Real-time Unit Sub System)
    > UIO driver which exports SOC resources associated with PRUSS like
    > I/O, memories and IRQs to user space. PRUSS is dual 32-bit RISC
    > processors which is efficient in performing embedded tasks that
    > require manipulation of packed memory mapped data structures and
    > efficient in handling system events that have tight real time
    > constraints. This driver is currently supported on Texas Instruments
    > DA850, AM18xx and OMAPL1-38 devices.
    > For example, PRUSS runs firmware for real-time critical industrial
    > communication data link layer and communicates with application stack
    > running in user space via shared memory and IRQs.

    Looks basically ok, but there are two limitations that I see that you
    might consider fixing.

    Oh, and you should put the Signed-off-by statement below the changelog,
    not above it, but that has nothing to do with the code.

    > +/*
    > + * Host event IRQ numbers from PRUSS
    > + * 3 PRU_EVTOUT0 PRUSS Interrupt
    > + * 4 PRU_EVTOUT1 PRUSS Interrupt
    > + * 5 PRU_EVTOUT2 PRUSS Interrupt
    > + * 6 PRU_EVTOUT3 PRUSS Interrupt
    > + * 7 PRU_EVTOUT4 PRUSS Interrupt
    > + * 8 PRU_EVTOUT5 PRUSS Interrupt
    > + * 9 PRU_EVTOUT6 PRUSS Interrupt
    > + * 10 PRU_EVTOUT7 PRUSS Interrupt
    > +*/
    > +
    > +#define MAX_PRUSS_EVTOUT_INSTANCE (8)
    > +
    > +static struct clk *pruss_clk;
    > +static struct uio_info *info[MAX_PRUSS_EVTOUT_INSTANCE];
    > +static void *ddr_virt_addr;
    > +static dma_addr_t ddr_phy_addr;

    By making all of these static variables, you limit youself to
    a single PRUSS instance in the system. It's generally better
    to write device drivers in a way that makes it possible to
    have multiple instances, e.g. by moving these four variables
    into the 'priv' part of struct uio_info.

    > +static irqreturn_t pruss_handler(int irq, struct uio_info *dev_info)
    > +{
    > + return IRQ_HANDLED;
    > +}

    An empty interrupt handler is rather pointless. I guess you really
    notify user space when the interrupt handler gets called, as this
    is the main point of a UIO driver as far as I understand it.

    Arnd


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