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SubjectRe: [RFC PATCH v2] fpga: Introduce new fpga subsystem
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On Wed, 2013-10-02 at 17:35 +0200, Michal Simek wrote:
> This new fpga subsystem core should unify all fpga drivers/managers which
> do the same things. Load configuration data to fpga or another programmable
> logic through common interface. It doesn't matter if it is MMIO device,
> gpio bitbanging, etc. connection. The point is to have the same
> interface for these drivers.

Does this interface support partial reprogramming/configuration
for FPGAs that can do that?

trivial notes:

There are a _lot_ of dev_dbg statements.

I hope some of these would be removed one day,
especially the function tracing style ones, because
there's already a generic kernel mechanism for that.

Maybe perf/trace support could be added eventually.

> diff --git a/drivers/fpga/fpga-mgr.c b/drivers/fpga/fpga-mgr.c
[]
> +/**
> + * fpga_mgr_status_write - Write fpga manager status
> + * @dev: Pointer to the device structure
> + * @attr: Pointer to the device attribute structure
> + * @buf: Pointer to the buffer location
> + * @count: Number of characters in @buf
> + *
> + * Returns the number of bytes copied to @buf, a negative error number otherwise
> + */
> +static ssize_t fpga_mgr_status_write(struct device *dev,
> + struct device_attribute *attr,
> + const char *buf, size_t count)
> +{
> + struct fpga_manager *mgr = dev_get_drvdata(dev);
> + int ret;
> +
> + if (test_and_set_bit_lock(FPGA_MGR_DEV_BUSY, &mgr->flags))
> + return -EBUSY;
> +
> + ret = strcmp(buf, "write_init");
> + if (!ret) {
> + ret = fpga_mgr_write_init(mgr);
> + goto out;
> + }
> +
> + ret = strcmp(buf, "write_complete");
> + if (!ret) {
> + ret = fpga_mgr_write_complete(mgr);
> + goto out;
> + }
> +
> + ret = strcmp(buf, "read_init");
> + if (!ret) {
> + ret = fpga_mgr_read_init(mgr);
> + goto out;
> + }
> +
> + ret = strcmp(buf, "read_complete");
> + if (!ret) {
> + ret = fpga_mgr_read_complete(mgr);
> + goto out;
> + }
> +
> + ret = -EINVAL;
> +out:
> + clear_bit_unlock(FPGA_MGR_DEV_BUSY, &mgr->flags);
> +
> + return ret ? : count;
> +}

I think this style is awkward and this would be
better written as:

if (!strcmp(buf, "write_init"))
ret = fpga_mgr_write_init(mgr);
else if (!strcmp(buf, "write_complete"))
ret = fpga_mgr_write_complete(mgr);
else if (!strcmp(buf, "read_init"))
ret = fpga_mgr_read_init(mgr);
else if (!strcmp(buf, "read_complete"))
ret = fpga_mgr_read_complete(mgr);
else
ret = -EINVAL;

clear_bit_unlock(FPGA_MGR_DEV_BUSY, &mgr->flags);

if (ret)
return ret;

return count;
}

Maybe use (strcmp(...) == 0) if you prefer that.
Both styles are commonly used in linux.

Probably all of the "return ret ?: count;" uses
would be more easily understood on 3 lines.




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