Hi,
I submitted this some time back but got no 'love' from the community[1]
so I'm reposting it.
Some hardware platforms, the TS-7800[2] is one for example, can supply
the kernel with an entropy source, albeit a slow one for TS-7800 users,
by just reading a particular IO address. This source must not be read
above a certain rate otherwise the quality is not suitable.
The driver is then hooked into by calling
platform_device_(register|add|del) passing a structure similar to:
------------
#define TS_RNG (TS78XX_FPGA_REGS_VIRT_BASE | 0x044)
static struct timeriomem_rng_data ts78xx_ts_rng_data = {
.address = (u32 *__iomem) TS_RNG,
.period = 1000000, /* one second */
};
static struct platform_device ts78xx_ts_rng_device = {
.name = "timeriomem_rng",
.id = -1,
.dev = {
.platform_data = &ts78xx_ts_rng_data,
},
.num_resources = 0,
};
------------
Feedback welcomed.
Cheers
Alex
[1] http://lkml.org/lkml/2008/6/15/106
[2] http://www.embeddedarm.com/products/board-detail.php?product=TS-7800
diff --git a/drivers/char/hw_random/Kconfig b/drivers/char/hw_random/Kconfig
index 8822eca..638e060 100644
--- a/drivers/char/hw_random/Kconfig
+++ b/drivers/char/hw_random/Kconfig
@@ -20,6 +20,19 @@ config HW_RANDOM
If unsure, say Y.
+config HW_RANDOM_TIMERIOMEM
+ tristate "Timer IOMEM HW Random Number Generator support"
+ depends on HW_RANDOM
+ ---help---
+ This driver provides kernel-side support for a generic Random
+ Number Generator provisioned by hardware through a 'dumb' iomem
+ address; for example the TS-7800 is such a device.
+
+ To compile this driver as a module, choose M here: the
+ module will be called timeriomem-rng.
+
+ If unsure, say Y.
+
config HW_RANDOM_INTEL
tristate "Intel HW Random Number Generator support"
depends on HW_RANDOM && (X86 || IA64) && PCI
diff --git a/drivers/char/hw_random/Makefile b/drivers/char/hw_random/Makefile
index b6effb7..e81d21a 100644
--- a/drivers/char/hw_random/Makefile
+++ b/drivers/char/hw_random/Makefile
@@ -4,6 +4,7 @@
obj-$(CONFIG_HW_RANDOM) += rng-core.o
rng-core-y := core.o
+obj-$(CONFIG_HW_RANDOM_TIMERIOMEM) += timeriomem-rng.o
obj-$(CONFIG_HW_RANDOM_INTEL) += intel-rng.o
obj-$(CONFIG_HW_RANDOM_AMD) += amd-rng.o
obj-$(CONFIG_HW_RANDOM_GEODE) += geode-rng.o
diff --git a/drivers/char/hw_random/timeriomem-rng.c b/drivers/char/hw_random/timeriomem-rng.c
new file mode 100644
index 0000000..42f2813
--- /dev/null
+++ b/drivers/char/hw_random/timeriomem-rng.c
@@ -0,0 +1,153 @@
+/*
+ * drivers/char/hw_random/timeriomem-rng.c
+ *
+ * Copyright (C) 2008 Alexander Clouter <[email protected]>
+ *
+ * Derived from drivers/char/hw_random/omap-rng.c
+ * Copyright 2005 (c) MontaVista Software, Inc.
+ * Author: Deepak Saxena <[email protected]>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * Overview:
+ * This driver is useful for platforms that have an IO range that provides
+ * periodic random data from a single IO memory address. All the platform
+ * has to do is provide the address and 'wait time' that new data becomes
+ * available.
+ *
+ * TODO: add support for reading sizes other than 32bits and masking
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/platform_device.h>
+#include <linux/hw_random.h>
+#include <linux/io.h>
+#include <linux/timeriomem-rng.h>
+#include <linux/jiffies.h>
+#include <linux/sched.h>
+#include <linux/timer.h>
+
+static struct timeriomem_rng_data *timeriomem_rng_data;
+
+static void timeriomem_rng_trigger(unsigned long);
+static DEFINE_TIMER(timeriomem_rng_timer, &timeriomem_rng_trigger, 0, 0);
+
+/*
+ * have data return 1, however return 0 if we have nothing
+ */
+static int timeriomem_rng_data_present(struct hwrng *rng, int wait)
+{
+ s32 delay;
+
+ if (rng->priv == 0)
+ return 1;
+
+ if (timer_pending(&timeriomem_rng_timer)) {
+ if (!wait)
+ return 0;
+
+ del_timer(&timeriomem_rng_timer);
+ delay = (long)timeriomem_rng_timer.expires - (long)jiffies;
+
+ schedule_timeout_uninterruptible(delay);
+ }
+
+ return 1;
+}
+
+static int timeriomem_rng_data_read(struct hwrng *rng, u32 *data)
+{
+ u32 cur;
+ s32 delay;
+
+ *data = *timeriomem_rng_data->address;
+
+ if (rng->priv != 0) {
+ cur = jiffies;
+
+ delay = (long)cur - (long)timeriomem_rng_timer.expires;
+ delay = rng->priv - (delay % rng->priv);
+
+ timeriomem_rng_timer.expires = cur + delay;
+ add_timer(&timeriomem_rng_timer);
+ }
+
+ return 4;
+}
+
+static void timeriomem_rng_trigger(unsigned long dummy)
+{
+ del_timer(&timeriomem_rng_timer);
+}
+
+static struct hwrng timeriomem_rng_ops = {
+ .name = "timeriomem",
+ .data_present = timeriomem_rng_data_present,
+ .data_read = timeriomem_rng_data_read,
+ .priv = 0,
+};
+
+static int __init timeriomem_rng_probe(struct platform_device *pdev)
+{
+ int ret;
+
+ timeriomem_rng_data = pdev->dev.platform_data;
+
+ if (timeriomem_rng_data->period != 0
+ && usecs_to_jiffies(timeriomem_rng_data->period) > 0) {
+ timeriomem_rng_timer.expires = jiffies;
+ init_timer(&timeriomem_rng_timer);
+
+ timeriomem_rng_ops.priv = usecs_to_jiffies(
+ timeriomem_rng_data->period);
+ }
+
+ ret = hwrng_register(&timeriomem_rng_ops);
+ if (ret) {
+ dev_err(&pdev->dev, "problem registering\n");
+ return ret;
+ }
+
+ dev_info(&pdev->dev, "32bits from 0x%p @ %dus\n",
+ timeriomem_rng_data->address,
+ timeriomem_rng_data->period);
+
+ return 0;
+}
+
+static int __devexit timeriomem_rng_remove(struct platform_device *pdev)
+{
+ del_timer(&timeriomem_rng_timer);
+ hwrng_unregister(&timeriomem_rng_ops);
+
+ return 0;
+}
+
+static struct platform_driver timeriomem_rng_driver = {
+ .driver = {
+ .name = "timeriomem_rng",
+ .owner = THIS_MODULE,
+ },
+ .probe = timeriomem_rng_probe,
+ .remove = __devexit_p(timeriomem_rng_remove),
+};
+
+static int __init timeriomem_rng_init(void)
+{
+ return platform_driver_register(&timeriomem_rng_driver);
+}
+
+static void __exit timeriomem_rng_exit(void)
+{
+ platform_driver_unregister(&timeriomem_rng_driver);
+}
+
+module_init(timeriomem_rng_init);
+module_exit(timeriomem_rng_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Alexander Clouter <[email protected]>");
+MODULE_DESCRIPTION("Timer IOMEM H/W RNG driver");
diff --git a/include/linux/timeriomem-rng.h b/include/linux/timeriomem-rng.h
new file mode 100644
index 0000000..16dd9e4
--- /dev/null
+++ b/include/linux/timeriomem-rng.h
@@ -0,0 +1,16 @@
+/*
+ * linux/include/linux/timeriomem-rng.h
+ *
+ * Copyright (c) 2008 Alexander Clouter <[email protected]>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+struct timeriomem_rng_data {
+ u32 __iomem *address;
+
+ /* measures in usecs */
+ unsigned int period;
+};
On Tue, 30 Dec 2008 14:52:10 +0000
Alexander Clouter <[email protected]> wrote:
> Hi,
>
> I submitted this some time back but got no 'love' from the community[1]
> so I'm reposting it.
>
> Some hardware platforms, the TS-7800[2] is one for example, can supply
> the kernel with an entropy source, albeit a slow one for TS-7800 users,
> by just reading a particular IO address. This source must not be read
> above a certain rate otherwise the quality is not suitable.
>
> The driver is then hooked into by calling
> platform_device_(register|add|del) passing a structure similar to:
> ------------
> #define TS_RNG (TS78XX_FPGA_REGS_VIRT_BASE | 0x044)
>
> static struct timeriomem_rng_data ts78xx_ts_rng_data = {
> .address = (u32 *__iomem) TS_RNG,
> .period = 1000000, /* one second */
> };
>
> static struct platform_device ts78xx_ts_rng_device = {
> .name = "timeriomem_rng",
> .id = -1,
> .dev = {
> .platform_data = &ts78xx_ts_rng_data,
> },
> .num_resources = 0,
> };
> ------------
>
questions...
> +++ b/drivers/char/hw_random/timeriomem-rng.c
> @@ -0,0 +1,153 @@
> +/*
> + * drivers/char/hw_random/timeriomem-rng.c
> + *
> + * Copyright (C) 2008 Alexander Clouter <[email protected]>
> + *
> + * Derived from drivers/char/hw_random/omap-rng.c
> + * Copyright 2005 (c) MontaVista Software, Inc.
> + * Author: Deepak Saxena <[email protected]>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * Overview:
> + * This driver is useful for platforms that have an IO range that provides
> + * periodic random data from a single IO memory address. All the platform
> + * has to do is provide the address and 'wait time' that new data becomes
> + * available.
> + *
> + * TODO: add support for reading sizes other than 32bits and masking
> + */
> +
> +#include <linux/module.h>
> +#include <linux/kernel.h>
> +#include <linux/platform_device.h>
> +#include <linux/hw_random.h>
> +#include <linux/io.h>
> +#include <linux/timeriomem-rng.h>
> +#include <linux/jiffies.h>
> +#include <linux/sched.h>
> +#include <linux/timer.h>
> +
> +static struct timeriomem_rng_data *timeriomem_rng_data;
> +
> +static void timeriomem_rng_trigger(unsigned long);
> +static DEFINE_TIMER(timeriomem_rng_timer, &timeriomem_rng_trigger, 0, 0);
> +
> +/*
> + * have data return 1, however return 0 if we have nothing
> + */
> +static int timeriomem_rng_data_present(struct hwrng *rng, int wait)
> +{
> + s32 delay;
> +
> + if (rng->priv == 0)
> + return 1;
> +
> + if (timer_pending(&timeriomem_rng_timer)) {
> + if (!wait)
> + return 0;
> +
> + del_timer(&timeriomem_rng_timer);
> + delay = (long)timeriomem_rng_timer.expires - (long)jiffies;
> +
> + schedule_timeout_uninterruptible(delay);
> + }
> +
> + return 1;
> +}
Would it be better (less racy) to do
if (del_timer(&timeriomem_rng_timer)) {
if (!wait)
return 0;
delay = (long)timeriomem_rng_timer.expires - (long)jiffies;
schedule_timeout_uninterruptible(delay);
}
Secondly, can `delay' be negative, if jiffies increments at just the
right (ie: wrong) time?
Thirdly, why the typecasts in the calculation of `delay'? Both terms
already have type `unsigned long'.
Fourthly, should it use del_timer_sync()? Bear in mind that the timer
handler might be concurrently running on another CPU.
> +static int timeriomem_rng_data_read(struct hwrng *rng, u32 *data)
> +{
> + u32 cur;
> + s32 delay;
> +
> + *data = *timeriomem_rng_data->address;
This is reading from I/O memory. It should use readl()?
> + if (rng->priv != 0) {
> + cur = jiffies;
> +
> + delay = (long)cur - (long)timeriomem_rng_timer.expires;
bug: `cur' should have type `unsigned long'. The u32 can get truncated.
Then, the casts are unneeded.
> + delay = rng->priv - (delay % rng->priv);
> +
> + timeriomem_rng_timer.expires = cur + delay;
> + add_timer(&timeriomem_rng_timer);
> + }
> +
> + return 4;
> +}
> +
> +static void timeriomem_rng_trigger(unsigned long dummy)
> +{
> + del_timer(&timeriomem_rng_timer);
> +}
del_timer_sync()?
> +static struct hwrng timeriomem_rng_ops = {
> + .name = "timeriomem",
> + .data_present = timeriomem_rng_data_present,
> + .data_read = timeriomem_rng_data_read,
> + .priv = 0,
> +};
> +
> +static int __init timeriomem_rng_probe(struct platform_device *pdev)
> +{
> + int ret;
> +
> + timeriomem_rng_data = pdev->dev.platform_data;
> +
> + if (timeriomem_rng_data->period != 0
> + && usecs_to_jiffies(timeriomem_rng_data->period) > 0) {
> + timeriomem_rng_timer.expires = jiffies;
> + init_timer(&timeriomem_rng_timer);
I don't think the init_timer() is needed - we already (correctly)
initialised it at compile time?
> + timeriomem_rng_ops.priv = usecs_to_jiffies(
> + timeriomem_rng_data->period);
> + }
> +
> + ret = hwrng_register(&timeriomem_rng_ops);
> + if (ret) {
> + dev_err(&pdev->dev, "problem registering\n");
> + return ret;
> + }
> +
> + dev_info(&pdev->dev, "32bits from 0x%p @ %dus\n",
> + timeriomem_rng_data->address,
> + timeriomem_rng_data->period);
> +
> + return 0;
> +}
What will happen if we load this driver on machines which don't
actually have the necessary hardware? Even non-x86 hardware?
> +static int __devexit timeriomem_rng_remove(struct platform_device *pdev)
> +{
> + del_timer(&timeriomem_rng_timer);
This should be del_timer_sync(). Otherwise the timer handler could be
running on another CPU during driver teardown.
> + hwrng_unregister(&timeriomem_rng_ops);
> +
> + return 0;
> +}
> +
> +static struct platform_driver timeriomem_rng_driver = {
> + .driver = {
> + .name = "timeriomem_rng",
> + .owner = THIS_MODULE,
> + },
> + .probe = timeriomem_rng_probe,
> + .remove = __devexit_p(timeriomem_rng_remove),
> +};
> +
> +static int __init timeriomem_rng_init(void)
> +{
> + return platform_driver_register(&timeriomem_rng_driver);
> +}
> +
> +static void __exit timeriomem_rng_exit(void)
> +{
> + platform_driver_unregister(&timeriomem_rng_driver);
> +}
> +
> +module_init(timeriomem_rng_init);
> +module_exit(timeriomem_rng_exit);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_AUTHOR("Alexander Clouter <[email protected]>");
> +MODULE_DESCRIPTION("Timer IOMEM H/W RNG driver");
> diff --git a/include/linux/timeriomem-rng.h b/include/linux/timeriomem-rng.h
> new file mode 100644
> index 0000000..16dd9e4
> --- /dev/null
> +++ b/include/linux/timeriomem-rng.h
> @@ -0,0 +1,16 @@
> +/*
> + * linux/include/linux/timeriomem-rng.h
> + *
> + * Copyright (c) 2008 Alexander Clouter <[email protected]>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + */
> +
> +struct timeriomem_rng_data {
> + u32 __iomem *address;
> +
> + /* measures in usecs */
> + unsigned int period;
> +};
Sorry for the slow reply. <insert-usual-excuses/>
Thanks though for picking this up and finding the time to have a nosey
at it.
* Andrew Morton <[email protected]> [Mon, 12 Jan 2009 13:13:21 -0800]:
>
>> +/*
>> + * have data return 1, however return 0 if we have nothing
>> + */
>> +static int timeriomem_rng_data_present(struct hwrng *rng, int wait)
>> +{
>> + s32 delay;
>> +
>> + if (rng->priv == 0)
>> + return 1;
>> +
>> + if (timer_pending(&timeriomem_rng_timer)) {
>> + if (!wait)
>> + return 0;
>> +
>> + del_timer(&timeriomem_rng_timer);
>> + delay = (long)timeriomem_rng_timer.expires - (long)jiffies;
>> +
>> + schedule_timeout_uninterruptible(delay);
>> + }
>> +
>> + return 1;
>> +}
>
> Would it be better (less racy) to do
>
> if (del_timer(&timeriomem_rng_timer)) {
> if (!wait)
> return 0;
>
> delay = (long)timeriomem_rng_timer.expires - (long)jiffies;
>
> schedule_timeout_uninterruptible(delay);
> }
>
Agreed.
> Secondly, can `delay' be negative, if jiffies increments at just the
> right (ie: wrong) time?
>
I thought long and hard about this when I initially put the code
together, I thought that it could only go very large (when jiffies
wraps) but never negative as I could not think of a case unless people
had a source that provided new data at intervals of time where jiffies
is larger than 2^32...hell you might as well not bother with that source
:)
Of course I should handle the wrap case, which I have already done at
least one (with an interval period of one second)...seemed to work fine.
> Thirdly, why the typecasts in the calculation of `delay'? Both terms
> already have type `unsigned long'.
>
Blind following of whats going on in linux/jiffies.h. If they can be
dropped then that's fine with me, I thought 'jiffies' was possibly
64bit on a platform or two (sparc64 and alpha for example).
> Fourthly, should it use del_timer_sync()? Bear in mind that the timer
> handler might be concurrently running on another CPU.
>
Will do, had no idea about that.
>> +static int timeriomem_rng_data_read(struct hwrng *rng, u32 *data)
>> +{
>> + u32 cur;
>> + s32 delay;
>> +
>> + *data = *timeriomem_rng_data->address;
>
> This is reading from I/O memory. It should use readl()?
>
Fixed.
>> + if (rng->priv != 0) {
>> + cur = jiffies;
>> +
>> + delay = (long)cur - (long)timeriomem_rng_timer.expires;
>
> bug: `cur' should have type `unsigned long'. The u32 can get truncated.
>
> Then, the casts are unneeded.
>
Fixed.
>> + delay = rng->priv - (delay % rng->priv);
>> +
>> + timeriomem_rng_timer.expires = cur + delay;
>> + add_timer(&timeriomem_rng_timer);
>> + }
>> +
>> + return 4;
>> +}
>> +
>> +static void timeriomem_rng_trigger(unsigned long dummy)
>> +{
>> + del_timer(&timeriomem_rng_timer);
>> +}
>
> del_timer_sync()?
>
Check.
>> +static struct hwrng timeriomem_rng_ops = {
>> + .name = "timeriomem",
>> + .data_present = timeriomem_rng_data_present,
>> + .data_read = timeriomem_rng_data_read,
>> + .priv = 0,
>> +};
>> +
>> +static int __init timeriomem_rng_probe(struct platform_device *pdev)
>> +{
>> + int ret;
>> +
>> + timeriomem_rng_data = pdev->dev.platform_data;
>> +
>> + if (timeriomem_rng_data->period != 0
>> + && usecs_to_jiffies(timeriomem_rng_data->period) > 0) {
>> + timeriomem_rng_timer.expires = jiffies;
>> + init_timer(&timeriomem_rng_timer);
>
> I don't think the init_timer() is needed - we already (correctly)
> initialised it at compile time?
>
Again, I had no idea, I was reading a tutorial on timers[1] and it said
init_timer(). "Just following orders capt'in".
I have removed the init_timer() and you are right, it is unneeded.
> What will happen if we load this driver on machines which don't
> actually have the necessary hardware? Even non-x86 hardware?
>
Cooks on my development ARM board with no problems, no idea if it works
on x86 though :) As for not having the hardware present, it's a platform
driver, surely it would be the fault of the crazed platform writer who
would to do something like this?
>> +static int __devexit timeriomem_rng_remove(struct platform_device *pdev)
>> +{
>> + del_timer(&timeriomem_rng_timer);
>
> This should be del_timer_sync(). Otherwise the timer handler could be
> running on another CPU during driver teardown.
>
Check.
Thanks again for having a look at my module. All I need is some further
feedback on the timer wrap bit (just ran it again now and it seems to
work still as expected after five minutes) and then I will re-submit.
Cheers
[1] http://lwn.net/images/pdf/LDD3/ch07.pdf
--
Alexander Clouter
.sigmonster says: Don't be overly suspicious where it's not warranted.