From: Ryan Mallon <ryan@bluewatersys.com>
To: Grant Likely <grant.likely@secretlab.ca>
Cc: Thomas Chou <thomas@wytron.com.tw>,
David Brownell <dbrownell@users.sourceforge.net>,
linux-kernel@vger.kernel.org, nios2-dev@sopc.et.ntust.edu.tw,
devicetree-discuss@lists.ozlabs.org,
spi-devel-general@lists.sourceforge.net
Subject: Re: [PATCH v9] spi: New driver for Altera SPI
Date: Wed, 16 Feb 2011 10:58:41 +1300 [thread overview]
Message-ID: <4D5AF711.3000508@bluewatersys.com> (raw)
In-Reply-To: <20110215194257.GB7649@angua.secretlab.ca>
On 16/02/11 08:42, Grant Likely wrote:
> On Tue, Feb 15, 2011 at 03:04:49PM +0800, Thomas Chou wrote:
>> Dear Ryan,
>>
>> On 02/14/2011 10:20 AM, Ryan Mallon wrote:
>>> On 02/14/2011 03:10 PM, Thomas Chou wrote:
>>>> This patch adds a new SPI driver to support the Altera SOPC Builder
>>>> SPI component. It uses the bitbanging library.
>>>>
>>>> Signed-off-by: Thomas Chou<thomas@wytron.com.tw>
>>>> ---
>>>> +struct altera_spi {
>>>> + /* bitbang has to be first */
>>>> + struct spi_bitbang bitbang;
>>> Is this still true? I had a quick look and can't see anything which
>>> relies on spi_bitbang being the first entry. Things like this should be
>>> using container_of so that position in the struct is irrelevant.
>>>
>>> ~Ryan
>>>
>> Yes, sadly true. This is due to the implementation of the bitbanging
>> library, spi_bitbang.c, which assumes the struct spi_bitbang is the
>> first of drvdata. Though it could be changed in the future (beyond
>> this little driver), every bitbanging library user has to follow
>> this for now.
> Should be easy to fix if it is indeed still true (I haven't dug deep
> enough to find the design error yet). Anybody want to volunteer?
>
> g.
>
The problem is that spi_master_get_devdata is used to get both
struct spi_bitbang and the controller dependent structure, which means
that struct spi_bitbang must be the first entry in the container
structure.
The following incomplete, untested patch shows a possible way to fix
this by introducing spi_alloc_master_bitbang. spi_master_get_devdata
now returns a pointer to struct spi_bitbang only. Drivers which need
an additional container struct should allocate it themselves and
pass the bitbang field to spi_alloc_master_bitbang. The driver
specific container can be fetched with:
static inline struct my_spi *to_my_spi(struct spi_master *master)
{
struct spi_bitbang *bitbang = spi_master_get_devdata(master);
return container_of(bitbang, struct my_spi, bitbang);
}
This patch only adds the alloc function and shows the necessary
changes to the spi_gpio.c driver, which is actually pretty minimal.
If there is any interest I can code up a proper patch.
~Ryan
---
diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 34bb17f..52ec691 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -27,6 +27,7 @@
#include <linux/slab.h>
#include <linux/mod_devicetable.h>
#include <linux/spi/spi.h>
+#include <linux/spi/spi_bitbang.h>
#include <linux/of_spi.h>
#include <linux/pm_runtime.h>
@@ -560,6 +561,24 @@ struct spi_master *spi_alloc_master(struct device *dev, unsigned size)
}
EXPORT_SYMBOL_GPL(spi_alloc_master);
+struct spi_master *spi_alloc_master_bitbang(struct device *dev,
+ struct spi_bitbang *bitbang)
+{
+ struct spi_master *master;
+
+ master = kzalloc(sizeof(struct spi_master), GFP_KERNEL);
+ if (!master)
+ return NULL;
+
+ device_initialize(&master->dev);
+ master->dev.class = &spi_master_class;
+ master->dev.parent = get_device(dev);
+ spi_master_set_devdata(master, bitbang);
+
+ return master;
+}
+EXPORT_SYMBOL_GPL(spi_alloc_master_bitbang);
+
/**
* spi_register_master - register SPI master controller
* @master: initialized master, originally from spi_alloc_master()
diff --git a/drivers/spi/spi_gpio.c b/drivers/spi/spi_gpio.c
index 63e51b0..169dbf0 100644
--- a/drivers/spi/spi_gpio.c
+++ b/drivers/spi/spi_gpio.c
@@ -329,12 +329,17 @@ static int __init spi_gpio_probe(struct platform_device *pdev)
if (status < 0)
return status;
- master = spi_alloc_master(&pdev->dev, sizeof *spi_gpio);
- if (!master) {
+ spi_gpio = kzalloc(sizeof(struct spi_gpio), GFP_KERNEL);
+ if (!spi_gpio) {
status = -ENOMEM;
goto gpio_free;
}
- spi_gpio = spi_master_get_devdata(master);
+
+ master = spi_alloc_master_bitbang(&pdev->dev, &spi_gpio->bitbang);
+ if (!master) {
+ status = -ENOMEM;
+ goto spi_gpio_free;
+ }
platform_set_drvdata(pdev, spi_gpio);
spi_gpio->pdev = pdev;
@@ -367,6 +372,8 @@ static int __init spi_gpio_probe(struct platform_device *pdev)
status = spi_bitbang_start(&spi_gpio->bitbang);
if (status < 0) {
spi_master_put(spi_gpio->bitbang.master);
+spi_gpio_free:
+ kfree(spi_gpio);
gpio_free:
if (SPI_MISO_GPIO != SPI_GPIO_NO_MISO)
gpio_free(SPI_MISO_GPIO);
@@ -391,6 +398,7 @@ static int __exit spi_gpio_remove(struct platform_device *pdev)
/* stop() unregisters child devices too */
status = spi_bitbang_stop(&spi_gpio->bitbang);
spi_master_put(spi_gpio->bitbang.master);
+ kfree(spi_gpio);
platform_set_drvdata(pdev, NULL);
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index b4d7710..3f72a34 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -336,7 +336,8 @@ static inline void spi_master_put(struct spi_master *master)
/* the spi driver core manages memory for the spi_master classdev */
extern struct spi_master *
spi_alloc_master(struct device *host, unsigned size);
-
+extern struct spi_master *
+spi_alloc_master_bitbang(struct device *host, struct spi_bitbang *bitbang);
extern int spi_register_master(struct spi_master *master);
extern void spi_unregister_master(struct spi_master *master);
next prev parent reply other threads:[~2011-02-15 21:58 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-10-08 6:03 [PATCH] spi: New driver for Altera SPI Thomas Chou
[not found] ` <1254981838-20584-1-git-send-email-thomas-SDxUXYEhEBiCuPEqFHbRBg@public.gmane.org>
2011-01-17 5:46 ` [PATCH v2] " Thomas Chou
[not found] ` <1295243200-28230-1-git-send-email-thomas-SDxUXYEhEBiCuPEqFHbRBg@public.gmane.org>
2011-01-17 5:59 ` Stephen Rothwell
[not found] ` <20110117165958.f89e8220.sfr-3FnU+UHB4dNDw9hX6IcOSA@public.gmane.org>
2011-01-17 6:22 ` Thomas Chou
[not found] ` <4D33E00E.5050802-SDxUXYEhEBiCuPEqFHbRBg@public.gmane.org>
2011-01-17 6:45 ` Grant Likely
[not found] ` <AANLkTi=D4Rcxbei2oo+EHc6X1O-2Oo+VWHAasK_JLj5W-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2011-01-17 7:04 ` [PATCH v3] " Thomas Chou
[not found] ` <1295247869-4968-1-git-send-email-thomas-SDxUXYEhEBiCuPEqFHbRBg@public.gmane.org>
2011-01-17 7:27 ` Sinan Akman
[not found] ` <4D33EF7C.7030005-w0xpxkV3uqlBDgjK7y7TUQ@public.gmane.org>
2011-01-18 1:33 ` Thomas Chou
2011-01-19 1:36 ` Thomas Chou
2011-01-17 6:56 ` [PATCH v2] " Grant Likely
[not found] ` <AANLkTimCvYai7mvrrHP9=EXB4L+yw3W2ad-7DU_iEzLy-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2011-01-17 7:13 ` [PATCH v4] " Thomas Chou
[not found] ` <1295248436-5049-1-git-send-email-thomas-SDxUXYEhEBiCuPEqFHbRBg@public.gmane.org>
2011-01-17 7:42 ` Grant Likely
[not found] ` <AANLkTinXduw54sKNa8r9sLm_Q8YjvpqAseYPhRshbNpE-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2011-01-24 6:38 ` [PATCH v5] " Thomas Chou
2011-02-03 10:02 ` [PATCH v6] " Thomas Chou
[not found] ` <1296727326-2581-1-git-send-email-thomas-SDxUXYEhEBiCuPEqFHbRBg@public.gmane.org>
2011-02-03 17:34 ` Grant Likely
2011-02-05 13:08 ` Thomas Chou
2011-02-05 14:02 ` [PATCH v7] " Thomas Chou
2011-02-06 20:23 ` Peter Korsgaard
[not found] ` <87aai8zzd1.fsf-uXGAPMMVk8amE9MCos8gUmSdvHPH+/yF@public.gmane.org>
2011-02-08 2:43 ` Thomas Chou
2011-02-08 5:21 ` [PATCH v8] " Thomas Chou
[not found] ` <1297142509-20158-1-git-send-email-thomas-SDxUXYEhEBiCuPEqFHbRBg@public.gmane.org>
2011-02-14 2:10 ` [PATCH v9] " Thomas Chou
2011-02-14 2:20 ` Ryan Mallon
[not found] ` <4D58917E.9050408-7Wk5F4Od5/oYd5yxfr4S2w@public.gmane.org>
2011-02-15 7:04 ` Thomas Chou
[not found] ` <4D5A2591.5090901-SDxUXYEhEBiCuPEqFHbRBg@public.gmane.org>
2011-02-15 9:12 ` Ryan Mallon
2011-02-15 19:42 ` Grant Likely
2011-02-15 21:58 ` Ryan Mallon [this message]
[not found] ` <1297649443-11491-1-git-send-email-thomas-SDxUXYEhEBiCuPEqFHbRBg@public.gmane.org>
2011-02-16 2:47 ` Grant Likely
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