Re: [RFC PATCH] fpga: Introduce new fpga subsystem

[Joe Perches <joe@perches.com>]

On Wed, 2013-09-18 at 17:56 +0200, Michal Simek wrote:
> This new subsystem should unify all fpga drivers 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
> inteface for these drivers.

Is this really a "driver".
Perhaps it's more of a core kernel function
and belongs in kernel.

> diff --git a/drivers/fpga/fpga-mgr.c b/drivers/fpga/fpga-mgr.c

The error messages are a little shouty with all
the unnecessary "!" uses.  

[]

> +/**
> + * fpga_mgr_read - Read data from fpga
> + * @mgr: Pointer to the fpga manager structure
> + * @buf: Pointer to the buffer location
> + * @count: Pointer to the number of copied bytes
> + *
> + * Function reads fpga bitstream and copy them to output buffer.
> + *
> + * Returns the number of bytes copied to @buf, a negative error number otherwise
> + */
> +static int fpga_mgr_read(struct fpga_manager *mgr, char *buf, ssize_t *count)
> +{
> +	int ret;
> +
> +	if (test_and_set_bit_lock(FPGA_MGR_DEV_BUSY, &mgr->flags))
> +		return -EBUSY;
> +
> +	if (!mgr->mops || !mgr->mops->read) {
> +		dev_err(mgr->dev,
> +			"Controller doesn't support read operations!\n");
> +		return -EPERM;
> +	}
> +
> +	if (mgr->mops->read_init) {
> +		ret = mgr->mops->read_init(mgr);
> +		if (ret) {
> +			dev_err(mgr->dev, "Failed in read-init!\n");
> +			return ret;
> +		}
> +	}
> +
> +	if (mgr->mops->read) {
> +		ret = mgr->mops->read(mgr, buf, count);
> +		if (ret) {
> +			dev_err(mgr->dev, "Failed to read firmware!\n");
> +			return ret;
> +		}
> +	}
> +
> +	if (mgr->mops->read_complete) {
> +		ret = mgr->mops->read_complete(mgr);
> +		if (ret) {
> +			dev_err(mgr->dev, "Failed in read-complete!\n");
> +			return ret;
> +		}
> +	}
> +
> +	clear_bit_unlock(FPGA_MGR_DEV_BUSY, &mgr->flags);
> +
> +	return 0;
> +}
> +
> +/**
> + * fpga_mgr_attr_read - Read data from fpga
> + * @dev: Pointer to the device structure
> + * @attr: Pointer to the device attribute structure
> + * @buf: Pointer to the buffer location
> + *
> + * Function reads fpga bitstream and copy them to output buffer
> + *
> + * Returns the number of bytes copied to @buf, a negative error number otherwise
> + */
> +static ssize_t fpga_mgr_attr_read(struct device *dev,
> +				   struct device_attribute *attr, char *buf)
> +{
> +	struct fpga_manager *mgr = dev_get_drvdata(dev);
> +	ssize_t count;
> +	int ret;
> +
> +	if (mgr && mgr->fpga_read)
> +		ret = mgr->fpga_read(mgr, buf, &count);
> +
> +	return ret == 0 ? count : -EPERM;

EPERM isn't the only error return from fpga_read.

> +}
> +
> +/**
> + * fpga_mgr_write - Write data to fpga
> + * @mgr: Pointer to the fpga manager structure
> + * @fw_name: Pointer to the buffer location with bistream firmware filename
> + *
> + * @buf contains firmware filename which is loading through firmware
> + * interface and passed to the fpga driver.
> + *
> + * Returns string lenght added to @fw_name, a negative error number otherwise
> + */
> +static int fpga_mgr_write(struct fpga_manager *mgr, const char *fw_name)
> +{
> +	int ret = 0;
> +	const struct firmware *fw;
> +
> +	if (!fw_name || !strlen(fw_name)) {
> +		dev_err(mgr->dev, "Firmware name is not specified!\n");
> +		return -EINVAL;
> +	}
> +
> +	if (!mgr->mops || !mgr->mops->write) {
> +		dev_err(mgr->dev,
> +			"Controller doesn't support write operations!\n");
> +		return -EPERM;

I think you should revisit the return codes.


> +/**
> + * fpga_mgr_attr_write - Write data to fpga
> + * @dev: Pointer to the device structure
> + * @attr: Pointer to the device attribute structure
> + * @buf: Pointer to the buffer location with bistream firmware filename
> + * @count: Number of characters in @buf
> + *
> + * @buf contains firmware filename which is loading through firmware
> + * interface and passed to the fpga driver.
> + *
> + * Returns string lenght added to @buf, a negative error number otherwise
> + */
> +static ssize_t fpga_mgr_attr_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 (mgr && mgr->fpga_write)
> +		ret = mgr->fpga_write(mgr, buf);
> +
> +	return ret == 0 ? strlen(buf) : -EPERM;
> +}

Same -EPERM issue as read

> +	mgr = devm_kzalloc(&pdev->dev, sizeof(*mgr), GFP_KERNEL);
> +	if (!mgr) {
> +		dev_err(&pdev->dev, "Failed to alloc mgr struct!\n");

Unnecessary OOM message as there's a general dump_stack()
already done on any OOM without GFP_NOWARN

> diff --git a/include/linux/fpga.h b/include/linux/fpga.h
[]
> +struct fpga_manager {
> +	char name[48];

Maybe a #define instead of 48?