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From: Lucas Tanure <tanure@linux.com>
To: Linux Kernel List <kernelnewbies@kernelnewbies.org>
Subject: Questions about mfd_add_devices and platform_data
Date: Thu, 1 Aug 2019 17:05:21 +0100
Message-ID: <CAJX_Q+2OmPa0jNG135z4zUCet=jVXnoaEQereT1oYcFPoWaWDg@mail.gmail.com> (raw)
In-Reply-To: <CACYKDtghiTsv8zGgoVvuQHqo=dmt_22GrK9xie-Y-3sNkiFfrw@mail.gmail.com>

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Hi,

I would like to understand mfd_add_devices call and platform_data section.

All the drivers I read the platform_data is static, but mfd_add_devices
will call platform_device_add_data which duplicates that memory and frees
the first pointer given.
But the first pointer is static and kfrees says:

"Don't free memory not originally allocated by kmalloc() or you will run
into trouble."

So, my questions is : Should my driver kmalloc platform_data first and then
call mfd_add_devices ? Or it's fine to give static memory to it ?

Example driver:

drivers/mfd/vexpress-sysreg.c:

static struct syscon_platform_data vexpress_sysreg_sys_id_pdata = {
.label = "sys_id",
};

static struct mfd_cell vexpress_sysreg_cells[] = {
{
.name = "syscon",
.num_resources = 1,
.resources = (struct resource []) {
DEFINE_RES_MEM(SYS_ID, 0x4),
},
.platform_data = &vexpress_sysreg_sys_id_pdata,
.pdata_size = sizeof(vexpress_sysreg_sys_id_pdata),
},

For this case mfd_add_devices will free vexpress_sysreg_sys_id_pdata, but
it's static.

Thanks
Lucas

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<div dir="ltr">Hi,<br><br>I would like to understand mfd_add_devices call and platform_data section. <br><br>All the drivers I read the platform_data is static, but mfd_add_devices will call platform_device_add_data which duplicates that memory and frees the first pointer given.<br>But the first pointer is static and kfrees says:<br><br>&quot;Don&#39;t free memory not originally allocated by kmalloc() or you will run into trouble.&quot;<br><br>So, my questions is : Should my driver kmalloc platform_data first and then call mfd_add_devices ? Or it&#39;s fine to give static memory to it ?<br><br>Example driver:<br><br>drivers/mfd/vexpress-sysreg.c:<br><br>static struct syscon_platform_data vexpress_sysreg_sys_id_pdata = {<br>	.label = &quot;sys_id&quot;,<br>};<br><br>static struct mfd_cell vexpress_sysreg_cells[] = {<br>	{<br>		.name = &quot;syscon&quot;,<br>		.num_resources = 1,<br>		.resources = (struct resource []) {<br>			DEFINE_RES_MEM(SYS_ID, 0x4),<br>		},<br>		.platform_data = &amp;vexpress_sysreg_sys_id_pdata,<br>		.pdata_size = sizeof(vexpress_sysreg_sys_id_pdata),<br>	},<br><br>For this case mfd_add_devices will free vexpress_sysreg_sys_id_pdata, but it&#39;s static.<br><br>Thanks<br>Lucas</div>

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Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-26 23:56 WOL from S5 (shutdown) Abu Rasheda
2019-07-31 19:32 ` Abu Rasheda
2019-08-01 16:05   ` Lucas Tanure [this message]

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