Messages in this thread Patch in this message | | | Subject | Re: [PATCH v2 2/3] platform/chrome: Support reading/writing the vboot context | From | Emilio López <> | Date | Tue, 15 Sep 2015 16:16:04 -0300 |
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Hi Javier,
Thanks for the review. You'll find my answers inline
On 15/09/15 10:47, Javier Martinez Canillas wrote: > Hello Emilio, > > Patch looks mostly good to me, I just have a few comments. > > On Mon, Sep 14, 2015 at 2:34 PM, Emilio López > <emilio.lopez@collabora.co.uk> wrote: >> Some EC implementations include a small nvram space used to store >> verified boot context data. This patch offers a way to expose this >> data to userspace. >> >> Signed-off-by: Emilio López <emilio.lopez@collabora.co.uk> >> --- >> Changes from v1: >> - Use is_bin_visible instead of is_visible >> >> Documentation/devicetree/bindings/mfd/cros-ec.txt | 4 + >> drivers/platform/chrome/Makefile | 5 +- >> drivers/platform/chrome/cros_ec_dev.c | 1 + >> drivers/platform/chrome/cros_ec_vbc.c | 137 ++++++++++++++++++++++ >> include/linux/mfd/cros_ec.h | 1 + >> 5 files changed, 147 insertions(+), 1 deletion(-) >> create mode 100644 drivers/platform/chrome/cros_ec_vbc.c >> >> diff --git a/Documentation/devicetree/bindings/mfd/cros-ec.txt b/Documentation/devicetree/bindings/mfd/cros-ec.txt >> index 1777916..136e0c2 100644 >> --- a/Documentation/devicetree/bindings/mfd/cros-ec.txt >> +++ b/Documentation/devicetree/bindings/mfd/cros-ec.txt >> @@ -34,6 +34,10 @@ Required properties (LPC): >> - compatible: "google,cros-ec-lpc" >> - reg: List of (IO address, size) pairs defining the interface uses >> >> +Optional properties (all): >> +- google,has-vbc-nvram: Some implementations of the EC include a small >> + nvram space used to store verified boot context data. This boolean flag >> + is used to specify whether this nvram is present or not. >> >> Example for I2C: >> > > I would split the DT binding part from the actual implementation, see > Documentation/devicetree/bindings/submitting-patches.txt.
Ok, I'll do
>> diff --git a/drivers/platform/chrome/Makefile b/drivers/platform/chrome/Makefile >> index 4a11b01..787be61 100644 >> --- a/drivers/platform/chrome/Makefile >> +++ b/drivers/platform/chrome/Makefile >> @@ -1,7 +1,10 @@ >> >> obj-$(CONFIG_CHROMEOS_LAPTOP) += chromeos_laptop.o >> obj-$(CONFIG_CHROMEOS_PSTORE) += chromeos_pstore.o >> -cros_ec_devs-objs := cros_ec_dev.o cros_ec_sysfs.o cros_ec_lightbar.o >> +cros_ec_devs-objs := cros_ec_dev.o >> +cros_ec_devs-objs += cros_ec_lightbar.o >> +cros_ec_devs-objs += cros_ec_sysfs.o >> +cros_ec_devs-objs += cros_ec_vbc.o > > Why are you changing the Makefile? AFAIK += is usually used when the > compilation is conditional based on a Kconfig symbol but since these > are build unconditionally, I'll just keep it as foo := bar baz
As far as I'm aware, += is append[0]. It's used for stuff like obj-$(CONFIG_CHROMEOS_LAPTOP) += chromeos_laptop.o because the left part will resolve to "obj-y" or similar, and you want to add to it, not replace it. I only changed the Makefile here because the line was growing too long, and I thought it looked neater this way; it shouldn't cause any functional change apart from the intended one.
[0] https://www.gnu.org/software/make/manual/html_node/Appending.html
> Which makes me think, do we need a Kconfig option for this feature > since not all machines have it?
Not all machines have a lightbar either; both of the features are runtime-conditional. IMO, it makes more sense this way when you consider a kernel will likely support multiple platforms.
>> obj-$(CONFIG_CROS_EC_CHARDEV) += cros_ec_devs.o >> obj-$(CONFIG_CROS_EC_LPC) += cros_ec_lpc.o >> obj-$(CONFIG_CROS_EC_PROTO) += cros_ec_proto.o >> diff --git a/drivers/platform/chrome/cros_ec_dev.c b/drivers/platform/chrome/cros_ec_dev.c >> index e8fcdc2..d19263f 100644 >> --- a/drivers/platform/chrome/cros_ec_dev.c >> +++ b/drivers/platform/chrome/cros_ec_dev.c >> @@ -32,6 +32,7 @@ static int ec_major; >> static const struct attribute_group *cros_ec_groups[] = { >> &cros_ec_attr_group, >> &cros_ec_lightbar_attr_group, >> + &cros_ec_vbc_attr_group, >> NULL, >> }; >> >> diff --git a/drivers/platform/chrome/cros_ec_vbc.c b/drivers/platform/chrome/cros_ec_vbc.c >> new file mode 100644 >> index 0000000..a0e8d38 >> --- /dev/null >> +++ b/drivers/platform/chrome/cros_ec_vbc.c >> @@ -0,0 +1,137 @@ >> +/* >> + * cros_ec_vbc - Expose the vboot context nvram to userspace >> + * >> + * Copyright (C) 2015 Collabora Ltd. >> + * >> + * based on vendor driver, >> + * >> + * Copyright (C) 2012 The Chromium OS Authors >> + * >> + * This program is free software; you can redistribute it and/or modify >> + * it under the terms of the GNU General Public License as published by >> + * the Free Software Foundation; either version 2 of the License, or >> + * (at your option) any later version. >> + * >> + * This program is distributed in the hope that it will be useful, >> + * but WITHOUT ANY WARRANTY; without even the implied warranty of >> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the >> + * GNU General Public License for more details. >> + */ >> + >> +#include <linux/of.h> >> +#include <linux/platform_device.h> >> +#include <linux/mfd/cros_ec.h> >> +#include <linux/mfd/cros_ec_commands.h> >> +#include <linux/slab.h> >> + >> +static ssize_t vboot_context_read(struct file *filp, struct kobject *kobj, >> + struct bin_attribute *att, char *buf, >> + loff_t pos, size_t count) >> +{ >> + struct device *dev = container_of(kobj, struct device, kobj); >> + struct cros_ec_dev *ec = container_of(dev, struct cros_ec_dev, >> + class_dev); >> + struct cros_ec_device *ecdev = ec->ec_dev; >> + struct ec_params_vbnvcontext *params; >> + struct cros_ec_command *msg; >> + int err; >> + const size_t para_sz = sizeof(struct ec_params_vbnvcontext); >> + const size_t resp_sz = sizeof(struct ec_response_vbnvcontext); >> + const size_t payload = max(para_sz, resp_sz); >> + >> + msg = kmalloc(sizeof(*msg) + payload, GFP_KERNEL); >> + if (!msg) >> + return -ENOMEM; >> + >> + params = (struct ec_params_vbnvcontext *)msg->data; >> + params->op = EC_VBNV_CONTEXT_OP_READ; >> + >> + msg->version = EC_VER_VBNV_CONTEXT; >> + msg->command = EC_CMD_VBNV_CONTEXT; >> + msg->outsize = sizeof(params->op); > Shouldn't this be para_sz ? Since you are sending to the EC the whole > struct ec_params_vbnvcontext and not only the op field. > > Or if the EC only expects to get the u32 op field, then I think your > max payload calculation is not correct.
The params struct is the same for both read and write ops, so it has the op flag and a buffer for the write op. During the read op I believe there's no need to send this potentially-garbage-filled buffer to the EC, so outsize is set accordingly here.
The vendor tree does it this way, but I can change it to send the full buffer if you prefer so.
ec code is at https://chromium.googlesource.com/chromiumos/platform/ec/+/master/common/system.c L1086+ if you want to take a look
>> + msg->insize = resp_sz; >> + >> + err = cros_ec_cmd_xfer(ecdev, msg); >> + if (err < 0) { >> + dev_err(dev, "Error sending read request: %d\n", err); >> + kfree(msg); >> + return err; >> + } >> + >> + BUILD_BUG_ON(resp_sz > PAGE_SIZE); > > Why you need this? struct ec_response_vbnvcontext is really small AFAICT.
This is just me being paranoid about memcpy :) Indeed, the struct should be way smaller than a page. I can drop it if you think it's too much.
>> + memcpy(buf, msg->data, resp_sz); >> + >> + kfree(msg); >> + return resp_sz; >> +} >> +
Thanks! Emilio
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