From: Michal Simek <michal.simek@xilinx.com>
To: Andrew Lunn <andrew@lunn.ch>, Michal Simek <michal.simek@xilinx.com>
Cc: monstr@monstr.eu, Al Cooper <alcooperx@gmail.com>,
Bastien Nocera <hadess@hadess.net>,
Piyush Mehta <piyush.mehta@xilinx.com>,
Masahiro Yamada <masahiroy@kernel.org>,
linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
Alan Stern <stern@rowland.harvard.edu>,
git@xilinx.com, "Alexander A. Klimov" <grandmaster@al2klimov.de>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 2/2] usb: misc: usb5744: Add support for USB hub controller
Date: Wed, 10 Feb 2021 12:03:56 +0100 [thread overview]
Message-ID: <58de4ddf-70e1-c20d-3d0f-c32b69f55ecd@xilinx.com> (raw)
In-Reply-To: <YCNKgAUi5d6LY6zf@lunn.ch>
Hi Andrew,
On 2/10/21 3:52 AM, Andrew Lunn wrote:
> On Tue, Feb 09, 2021 at 10:53:20AM +0100, Michal Simek wrote:
>> +static int usb5744_i2c_probe(struct i2c_client *client,
>> + const struct i2c_device_id *id)
>> +{
>> + struct device *dev = &client->dev;
>> + int ret;
>> +
>> + /* Trigger gpio reset to the hub. */
>> + ret = usb5744_init_hw(dev);
>> + if (ret)
>> + return ret;
>> +
>> + /* Send SMBus command to boot hub. */
>> + ret = i2c_smbus_write_word_data(client, 0xAA, swab16(0x5600));
>
> Hi Michal
>
> This is not my area of the kernel. But that swab16() stood out, and
> made me wonder about endianness. Will this work correctly on big and
> little endian hosts?
thanks for bringing this up. I didn't test it on BE system.
I have grepped the kernel
[linux](xnext/usb5744)$ git grep i2c_smbus_write_word_data | grep swab
drivers/media/i2c/uda1342.c:17: i2c_smbus_write_word_data(client, reg,
swab16(value));
drivers/media/i2c/vpx3220.c:97: if (i2c_smbus_write_word_data(client,
0x27, swab16(fpaddr)) == -1) {
drivers/media/i2c/vpx3220.c:106: if (i2c_smbus_write_word_data(client,
0x28, swab16(data)) == -1) {
drivers/media/i2c/vpx3220.c:120: if (i2c_smbus_write_word_data(client,
0x26, swab16(fpaddr)) == -1) {
drivers/usb/misc/usb5744.c:50: ret = i2c_smbus_write_word_data(client,
0xAA, swab16(0x5600));
include/linux/i2c.h:168: return i2c_smbus_write_word_data(client,
command, swab16(value));
And last one is interesting
164 static inline s32
165 i2c_smbus_write_word_swapped(const struct i2c_client *client,
166 u8 command, u16 value)
167 {
168 return i2c_smbus_write_word_data(client, command,
swab16(value));
169 }
And this function is also used
[linux](xnext/usb5744)$ git grep i2c_smbus_write_word_swapped | wc -l
76
I think it would be the best to test it and see if this code works on BE
but I need to prepare it first.
And current code is aligned with others but it doesn't mean that it is
correct.
Thanks,
Michal
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prev parent reply other threads:[~2021-02-10 11:05 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-09 9:53 [PATCH 0/2] usb: misc: Add support for Microchip USB5744 Michal Simek
2021-02-09 9:53 ` [PATCH 1/2] dt-bindings: usb: misc: Add binding for Microchip usb5744 hub Michal Simek
2021-02-09 9:53 ` [PATCH 2/2] usb: misc: usb5744: Add support for USB hub controller Michal Simek
2021-02-09 10:03 ` Greg Kroah-Hartman
2021-02-09 10:11 ` Michal Simek
2021-02-09 10:40 ` Greg Kroah-Hartman
2021-02-10 2:52 ` Andrew Lunn
2021-02-10 11:03 ` Michal Simek [this message]
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