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

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Message-ID: <alpine.DEB.2.02.1412181447160.25208@linuxheads99>
Date:	Thu, 18 Dec 2014 14:50:09 -0600
From:	atull <atull@...nsource.altera.com>
To:	Grant Likely <grant.likely@...aro.org>
CC:	Pavel Machek <pavel@...x.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	"Michal Simek" <monstr@...str.eu>,
	Michal Simek <michal.simek@...inx.com>,
	"Randy Dunlap" <rdunlap@...radead.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
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	Pantelis Antoniou <pantelis.antoniou@...sulko.com>,
	Rob Herring <robh+dt@...nel.org>,
	"Ira Snyder" <iws@...o.caltech.edu>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	Mark Brown <broonie@...nel.org>, <philip@...ister.org>,
	rubini <rubini@...dd.com>,
	Steffen Trumtrar <s.trumtrar@...gutronix.de>,
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	Andrew Morton <akpm@...ux-foundation.org>,
	"Linus Walleij" <linus.walleij@...aro.org>,
	Alan Tull <delicious.quinoa@...il.com>,
	<dinguyen@...nsource.altera.com>,
	Yves Vandervennet <yvanderv@...nsource.altera.com>
Subject: Re: [PATCH v2 2/3] fpga manager: framework core

On Sat, 6 Dec 2014, Grant Likely wrote:

> >> +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?
> 
> Custom locking schemes are just wrong. A mutex is the right thing to
> do here and then an -EBUSY isn't required.
> 

I've changed it to a mutex in the next version.

> >
> >> +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];
> 
> Hard coding a string length is a warning sign. That is the sort of
> thing that can memdup() or strdup() can handle.
> 

OK, I'll fix it using kstrdup() in v6.

Alan
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