Messages in this thread Patch in this message | | | Date | Wed, 2 Jan 2013 08:29:57 +0100 (CET) | From | Julia Lawall <> | Subject | Re: [PATCH RESEND 6/6] clk: s5p-g2d: Fix incorrect usage of IS_ERR_OR_NULL |
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On Wed, 2 Jan 2013, Tony Prisk wrote:
> On Wed, 2013-01-02 at 08:10 +0300, Dan Carpenter wrote: >> clk_get() returns NULL if CONFIG_HAVE_CLK is disabled. >> >> I told Tony about this but everyone has been gone with end of year >> holidays so it hasn't been addressed. >> >> Tony, please fix it so people don't apply these patches until >> clk_get() is updated to not return NULL. It sucks to have to revert >> patches. >> >> regards, >> dan carpenter > > I posted the query to Mike Turquette, linux-kernel and linux-arm-kernel > mailing lists, regarding the return of NULL when HAVE_CLK is undefined. > > Short Answer: A return value of NULL is valid and not an error therefore > we should be using IS_ERR, not IS_ERR_OR_NULL on clk_get results. > > I see the obvious problem this creates, and asked this question: > > If the driver can't operate with a NULL clk, it should use a > IS_ERR_OR_NULL test to test for failure, rather than IS_ERR. > > > And Russell's answer: > > Why should a _consumer_ of a clock care? It is _very_ important that > people get this idea - to a consumer, the struct clk is just an opaque > cookie. The fact that it appears to be a pointer does _not_ mean that > the driver can do any kind of dereferencing on that pointer - it should > never do so. > > Thread can be viewed here: > https://lkml.org/lkml/2012/12/20/105
There are dereferences to the result of clk_get a few times. I tried the following semantic patch:
@@ expression E; identifier I; @@ * E = clk_get(...) ... E->I
It gives the results shown below (- marks matched lines, not lines to remove). I also tried with devm_clk_get instead of clk_get, but got nothing.
julia
diff -u -p /var/linuxes/linux-next/arch/sh/kernel/cpufreq.c /tmp/nothing/arch/sh/kernel/cpufreq.c --- /var/linuxes/linux-next/arch/sh/kernel/cpufreq.c +++ /tmp/nothing/arch/sh/kernel/cpufreq.c @@ -117,15 +117,11 @@ static int sh_cpufreq_cpu_init(struct cp
dev = get_cpu_device(cpu);
- cpuclk = clk_get(dev, "cpu_clk"); - if (IS_ERR(cpuclk)) { dev_err(dev, "couldn't get CPU clk\n"); return PTR_ERR(cpuclk); }
- policy->cur = policy->min = policy->max = sh_cpufreq_get(cpu);
- freq_table = cpuclk->nr_freqs ? cpuclk->freq_table : NULL; if (freq_table) { int result;
diff -u -p /var/linuxes/linux-next/arch/mips/kernel/cpufreq/loongson2_cpufreq.c /tmp/nothing/arch/mips/kernel/cpufreq/loongson2_cpufreq.c --- /var/linuxes/linux-next/arch/mips/kernel/cpufreq/loongson2_cpufreq.c +++ /tmp/nothing/arch/mips/kernel/cpufreq/loongson2_cpufreq.c @@ -111,13 +111,10 @@ static int loongson2_cpufreq_cpu_init(st if (!cpu_online(policy->cpu)) return -ENODEV;
- cpuclk = clk_get(NULL, "cpu_clk"); - if (IS_ERR(cpuclk)) { printk(KERN_ERR "cpufreq: couldn't get CPU clk\n"); return PTR_ERR(cpuclk); }
- cpuclk->rate = cpu_clock_freq / 1000; if (!cpuclk->rate) return -EINVAL;
diff -u -p /var/linuxes/linux-next/drivers/net/ethernet/ti/cpts.c /tmp/nothing/drivers/net/ethernet/ti/cpts.c --- /var/linuxes/linux-next/drivers/net/ethernet/ti/cpts.c +++ /tmp/nothing/drivers/net/ethernet/ti/cpts.c @@ -241,14 +241,10 @@ static void cpts_overflow_check(struct w
static void cpts_clk_init(struct cpts *cpts) { - cpts->refclk = clk_get(NULL, CPTS_REF_CLOCK_NAME); - if (IS_ERR(cpts->refclk)) { pr_err("Failed to clk_get %s\n", CPTS_REF_CLOCK_NAME); cpts->refclk = NULL; return; } - clk_enable(cpts->refclk); - cpts->freq = cpts->refclk->recalc(cpts->refclk); }
static void cpts_clk_release(struct cpts *cpts) diff -u -p /var/linuxes/linux-next/drivers/i2c/busses/i2c-sh7760.c /tmp/nothing/drivers/i2c/busses/i2c-sh7760.c --- /var/linuxes/linux-next/drivers/i2c/busses/i2c-sh7760.c +++ /tmp/nothing/drivers/i2c/busses/i2c-sh7760.c @@ -397,11 +397,7 @@ static int calc_CCR(unsigned long scl_hz signed char cdf, cdfm; int scgd, scgdm, scgds;
- mclk = clk_get(NULL, "peripheral_clk"); - if (IS_ERR(mclk)) { return PTR_ERR(mclk); - } else { - mck = mclk->rate; clk_put(mclk); }
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