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

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Message-Id: <B914D894-E486-4EF1-8F84-169E939C58B4@konsulko.com>
Date:	Fri, 24 Oct 2014 13:55:10 +0300
From:	Pantelis Antoniou <pantelis.antoniou@...sulko.com>
To:	Pavel Machek <pavel@...x.de>
Cc:	atull@...nsource.altera.com,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	jgunthorpe@...idianresearch.com, hpa@...or.com,
	Michal Simek <monstr@...str.eu>, michal.simek@...inx.com,
	rdunlap@...radead.org, linux-kernel <linux-kernel@...r.kernel.org>,
	devicetree@...r.kernel.org, robh+dt@...nel.org,
	Grant Likely <grant.likely@...aro.org>, iws@...o.caltech.edu,
	linux-doc@...r.kernel.org, Mark Brown <broonie@...nel.org>,
	philip@...ister.org, rubini@...dd.com,
	Steffen Trumtrar <s.trumtrar@...gutronix.de>,
	jason@...edaemon.net, kyle.teske@...com, nico@...aro.org,
	Felipe Balbi <balbi@...com>, m.chehab@...sung.com,
	davidb@...eaurora.org, Rob Landley <rob@...dley.net>,
	davem@...emloft.net, cesarb@...arb.net, sameo@...ux.intel.com,
	akpm@...ux-foundation.org,
	Linus Walleij <linus.walleij@...aro.org>,
	Alan Tull <delicious.quinoa@...il.com>,
	dinguyen@...nsource.altera.com, yvanderv@...nsource.altera.com
Subject: Re: [PATCH v2 2/3] fpga manager: framework core

Hi Pavel,

> On Oct 24, 2014, at 1:52 PM, Pavel Machek <pavel@...x.de> wrote:
> 
> 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?
> 

FWIW the overlays patchset uses binary configfs attribute to make this work.

>> +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.
> 

I could argue that a valid firmware file is one that’s well formed and does not
contain those characters.

I guess this is only for make echo file >foo work. You could specify that echo -n file >foo is
required.


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

Regards

— Pantelis

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