linux-kernel - Re: [PATCH v2 2/3] fpga manager: framework core

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Date:	Fri, 24 Oct 2014 12:52:00 +0200
From:	Pavel Machek <pavel@...x.de>
To:	atull@...nsource.altera.com
Cc:	gregkh@...uxfoundation.org, jgunthorpe@...idianresearch.com,
	hpa@...or.com, monstr@...str.eu, michal.simek@...inx.com,
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Subject: Re: [PATCH v2 2/3] fpga manager: framework core

Hi!

> * /sys/class/fpga_manager/<fpga>/firmware
>   Name of FPGA image file to load using firmware class.
>   $ echo image.rbf > /sys/class/fpga_manager/<fpga>/firmware

I .. still don't think this is good idea. What about namespaces?
The path corresponds to path in which namespace?

> +int fpga_mgr_write(struct fpga_manager *mgr, const char *buf, size_t count)
> +{
> +	int ret;
> +
> +	if (test_and_set_bit_lock(FPGA_MGR_BUSY, &mgr->flags))
> +		return -EBUSY;
> +
> +	dev_info(mgr->dev, "writing buffer to %s\n", mgr->name);
> +
> +	ret = __fpga_mgr_write(mgr, buf, count);
> +	clear_bit_unlock(FPGA_MGR_BUSY, &mgr->flags);
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(fpga_mgr_write);

Is the EBUSY -- userspace please try again, but you don't know when to
try again -- right interface? I mean, normally kernel would wait, so
that userland does not have to poll?

> +static ssize_t fpga_mgr_firmware_store(struct device *dev,
> +				       struct device_attribute *attr,
> +				       const char *buf, size_t count)
> +{
> +	struct fpga_manager *mgr = dev_get_drvdata(dev);
> +	unsigned int len;
> +	char image_name[NAME_MAX];
> +	int ret;
> +
> +	/* lose terminating \n */
> +	strcpy(image_name, buf);
> +	len = strlen(image_name);
> +	if (image_name[len - 1] == '\n')
> +		image_name[len - 1] = 0;
> +
> +	ret = fpga_mgr_firmware_write(mgr, image_name);
> +	if (ret)
> +		return ret;
> +
> +	return count;
> +}

This shows why the interface is not right... Valid filename may
contain \n, right? It may even end with \n.

Best regards,
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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