Re: [PATCH v2 2/3] net: qrtr: Add MHI transport layer

Re: [PATCH v2 2/3] net: qrtr: Add MHI transport layer

[Markus Elfring]

> Hence, this commit adds MHI transport layer support to QRTR for
> transferring the QMI messages over IPC Router.

I suggest to reconsider software development consequences around
another implementation detail.


…
> +static int qcom_mhi_qrtr_send(struct qrtr_endpoint *ep, struct sk_buff *skb)
> +{
…
> +	rc = mhi_queue_skb(qdev->mhi_dev, DMA_TO_DEVICE, skb, skb->len,
> +			   MHI_EOT);
> +	if (rc) {
> +		kfree_skb(skb);
> +		return rc;
> +	}
…
> +}

I propose again to add a jump target so that a bit of exception handling code
can be better reused at the end of this function implementation.
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/coding-style.rst?id=b2768df24ec400dd4f7fa79542f797e904812053#n450

+	if (rc)
+		goto free_skb;
…
+	return rc;
+
+free_skb:
+	kfree_skb(skb);
+	return rc;
+}


Regards,
Markus

Re: [PATCH v2 2/3] net: qrtr: Add MHI transport layer

[Manivannan Sadhasivam]

On Sun, Apr 26, 2020 at 03:45:41PM +0200, Markus Elfring wrote:
> > Hence, this commit adds MHI transport layer support to QRTR for
> > transferring the QMI messages over IPC Router.
> 
> I suggest to reconsider software development consequences around
> another implementation detail.
> 
> 
> …
> > +static int qcom_mhi_qrtr_send(struct qrtr_endpoint *ep, struct sk_buff *skb)
> > +{
> …
> > +	rc = mhi_queue_skb(qdev->mhi_dev, DMA_TO_DEVICE, skb, skb->len,
> > +			   MHI_EOT);
> > +	if (rc) {
> > +		kfree_skb(skb);
> > +		return rc;
> > +	}
> …
> > +}
> 
> I propose again to add a jump target so that a bit of exception handling code
> can be better reused at the end of this function implementation.
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/coding-style.rst?id=b2768df24ec400dd4f7fa79542f797e904812053#n450
> 

Matter of taste! goto's are really useful if there are multiple exit paths
available. But in this case there is only one and I don't think we may add
anymore in future. So I'll keep it as it is.

Thanks,
Mani

> +	if (rc)
> +		goto free_skb;
> …
> +	return rc;
> +
> +free_skb:
> +	kfree_skb(skb);
> +	return rc;
> +}
> 
> 
> Regards,
> Markus

Re: [v2 2/3] net: qrtr: Add MHI transport layer

[Markus Elfring]

>> I propose again to add a jump target so that a bit of exception handling code
>> can be better reused at the end of this function implementation.
>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/coding-style.rst?id=b2768df24ec400dd4f7fa79542f797e904812053#n450
>>
>
> Matter of taste! goto's are really useful if there are multiple exit paths
> available. But in this case there is only one and I don't think we may add
> anymore in future. So I'll keep it as it is.

Do you hope that an other optimiser software will avoid duplicate code
like kfree_skb(skb) calls from if branches?

Regards,
Markus

Re: [v2 2/3] net: qrtr: Add MHI transport layer

[Manivannan Sadhasivam]

On 27 April 2020 12:20:43 PM IST, Markus Elfring <Markus.Elfring@web.de> wrote:
>>> I propose again to add a jump target so that a bit of exception
>handling code
>>> can be better reused at the end of this function implementation.
>>>
>https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/coding-style.rst?id=b2768df24ec400dd4f7fa79542f797e904812053#n450
>>>
>>
>> Matter of taste! goto's are really useful if there are multiple exit
>paths
>> available. But in this case there is only one and I don't think we
>may add
>> anymore in future. So I'll keep it as it is.
>
>Do you hope that an other optimiser software will avoid duplicate code
>like kfree_skb(skb) calls from if branches?
>

Doh. I didn't notice the previous kfree in skb_linearize(). Will spin v3 incorporating this change. 

Thanks, 
Mani

>Regards,
>Markus

-- 
Sent from my Android device with K-9 Mail. Please excuse my brevity.

[PATCH v2 2/3] net: qrtr: Add MHI transport layer

[Manivannan Sadhasivam]

MHI is the transport layer used for communicating to the external modems.
Hence, this commit adds MHI transport layer support to QRTR for
transferring the QMI messages over IPC Router.

Cc: "David S. Miller" <davem@davemloft.net>
Cc: netdev@vger.kernel.org
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
---
 net/qrtr/Kconfig  |   7 +++
 net/qrtr/Makefile |   2 +
 net/qrtr/mhi.c    | 126 ++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 135 insertions(+)
 create mode 100644 net/qrtr/mhi.c

diff --git a/net/qrtr/Kconfig b/net/qrtr/Kconfig
index 63f89cc6e82c..8eb876471564 100644
--- a/net/qrtr/Kconfig
+++ b/net/qrtr/Kconfig
@@ -29,4 +29,11 @@ config QRTR_TUN
 	  implement endpoints of QRTR, for purpose of tunneling data to other
 	  hosts or testing purposes.
 
+config QRTR_MHI
+	tristate "MHI IPC Router channels"
+	depends on MHI_BUS
+	help
+	  Say Y here to support MHI based ipcrouter channels. MHI is the
+	  transport used for communicating to external modems.
+
 endif # QRTR
diff --git a/net/qrtr/Makefile b/net/qrtr/Makefile
index 32d4e923925d..1b1411d158a7 100644
--- a/net/qrtr/Makefile
+++ b/net/qrtr/Makefile
@@ -5,3 +5,5 @@ obj-$(CONFIG_QRTR_SMD) += qrtr-smd.o
 qrtr-smd-y	:= smd.o
 obj-$(CONFIG_QRTR_TUN) += qrtr-tun.o
 qrtr-tun-y	:= tun.o
+obj-$(CONFIG_QRTR_MHI) += qrtr-mhi.o
+qrtr-mhi-y	:= mhi.o
diff --git a/net/qrtr/mhi.c b/net/qrtr/mhi.c
new file mode 100644
index 000000000000..2f604dff93cd
--- /dev/null
+++ b/net/qrtr/mhi.c
@@ -0,0 +1,126 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2018-2020, The Linux Foundation. All rights reserved.
+ */
+
+#include <linux/mhi.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/skbuff.h>
+#include <net/sock.h>
+
+#include "qrtr.h"
+
+struct qrtr_mhi_dev {
+	struct qrtr_endpoint ep;
+	struct mhi_device *mhi_dev;
+	struct device *dev;
+};
+
+/* From MHI to QRTR */
+static void qcom_mhi_qrtr_dl_callback(struct mhi_device *mhi_dev,
+				      struct mhi_result *mhi_res)
+{
+	struct qrtr_mhi_dev *qdev = dev_get_drvdata(&mhi_dev->dev);
+	int rc;
+
+	if (!qdev || mhi_res->transaction_status)
+		return;
+
+	rc = qrtr_endpoint_post(&qdev->ep, mhi_res->buf_addr,
+				mhi_res->bytes_xferd);
+	if (rc == -EINVAL)
+		dev_err(qdev->dev, "invalid ipcrouter packet\n");
+}
+
+/* From QRTR to MHI */
+static void qcom_mhi_qrtr_ul_callback(struct mhi_device *mhi_dev,
+				      struct mhi_result *mhi_res)
+{
+	struct sk_buff *skb = (struct sk_buff *)mhi_res->buf_addr;
+
+	if (skb->sk)
+		sock_put(skb->sk);
+	consume_skb(skb);
+}
+
+/* Send data over MHI */
+static int qcom_mhi_qrtr_send(struct qrtr_endpoint *ep, struct sk_buff *skb)
+{
+	struct qrtr_mhi_dev *qdev = container_of(ep, struct qrtr_mhi_dev, ep);
+	int rc;
+
+	rc = skb_linearize(skb);
+	if (rc) {
+		kfree_skb(skb);
+		return rc;
+	}
+
+	rc = mhi_queue_skb(qdev->mhi_dev, DMA_TO_DEVICE, skb, skb->len,
+			   MHI_EOT);
+	if (rc) {
+		kfree_skb(skb);
+		return rc;
+	}
+
+	if (skb->sk)
+		sock_hold(skb->sk);
+
+	return rc;
+}
+
+static int qcom_mhi_qrtr_probe(struct mhi_device *mhi_dev,
+			       const struct mhi_device_id *id)
+{
+	struct qrtr_mhi_dev *qdev;
+	int rc;
+
+	qdev = devm_kzalloc(&mhi_dev->dev, sizeof(*qdev), GFP_KERNEL);
+	if (!qdev)
+		return -ENOMEM;
+
+	qdev->mhi_dev = mhi_dev;
+	qdev->dev = &mhi_dev->dev;
+	qdev->ep.xmit = qcom_mhi_qrtr_send;
+
+	dev_set_drvdata(&mhi_dev->dev, qdev);
+	rc = qrtr_endpoint_register(&qdev->ep, QRTR_EP_NID_AUTO);
+	if (rc)
+		return rc;
+
+	dev_dbg(qdev->dev, "Qualcomm MHI QRTR driver probed\n");
+
+	return 0;
+}
+
+static void qcom_mhi_qrtr_remove(struct mhi_device *mhi_dev)
+{
+	struct qrtr_mhi_dev *qdev = dev_get_drvdata(&mhi_dev->dev);
+
+	qrtr_endpoint_unregister(&qdev->ep);
+	dev_set_drvdata(&mhi_dev->dev, NULL);
+}
+
+static const struct mhi_device_id qcom_mhi_qrtr_id_table[] = {
+	{ .chan = "IPCR" },
+	{}
+};
+MODULE_DEVICE_TABLE(mhi, qcom_mhi_qrtr_id_table);
+
+static struct mhi_driver qcom_mhi_qrtr_driver = {
+	.probe = qcom_mhi_qrtr_probe,
+	.remove = qcom_mhi_qrtr_remove,
+	.dl_xfer_cb = qcom_mhi_qrtr_dl_callback,
+	.ul_xfer_cb = qcom_mhi_qrtr_ul_callback,
+	.id_table = qcom_mhi_qrtr_id_table,
+	.driver = {
+		.name = "qcom_mhi_qrtr",
+	},
+};
+
+module_mhi_driver(qcom_mhi_qrtr_driver);
+
+MODULE_AUTHOR("Chris Lew <clew@codeaurora.org>");
+MODULE_AUTHOR("Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>");
+MODULE_DESCRIPTION("Qualcomm IPC-Router MHI interface driver");
+MODULE_LICENSE("GPL v2");
-- 
2.17.1

Re: [PATCH v2 2/3] net: qrtr: Add MHI transport layer

[Bjorn Andersson]

On Wed 01 Apr 22:36 PDT 2020, Manivannan Sadhasivam wrote:

> MHI is the transport layer used for communicating to the external modems.
> Hence, this commit adds MHI transport layer support to QRTR for
> transferring the QMI messages over IPC Router.
> 

Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>

Regards,
Bjorn

> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: netdev@vger.kernel.org
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
> ---
>  net/qrtr/Kconfig  |   7 +++
>  net/qrtr/Makefile |   2 +
>  net/qrtr/mhi.c    | 126 ++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 135 insertions(+)
>  create mode 100644 net/qrtr/mhi.c
> 
> diff --git a/net/qrtr/Kconfig b/net/qrtr/Kconfig
> index 63f89cc6e82c..8eb876471564 100644
> --- a/net/qrtr/Kconfig
> +++ b/net/qrtr/Kconfig
> @@ -29,4 +29,11 @@ config QRTR_TUN
>  	  implement endpoints of QRTR, for purpose of tunneling data to other
>  	  hosts or testing purposes.
>  
> +config QRTR_MHI
> +	tristate "MHI IPC Router channels"
> +	depends on MHI_BUS
> +	help
> +	  Say Y here to support MHI based ipcrouter channels. MHI is the
> +	  transport used for communicating to external modems.
> +
>  endif # QRTR
> diff --git a/net/qrtr/Makefile b/net/qrtr/Makefile
> index 32d4e923925d..1b1411d158a7 100644
> --- a/net/qrtr/Makefile
> +++ b/net/qrtr/Makefile
> @@ -5,3 +5,5 @@ obj-$(CONFIG_QRTR_SMD) += qrtr-smd.o
>  qrtr-smd-y	:= smd.o
>  obj-$(CONFIG_QRTR_TUN) += qrtr-tun.o
>  qrtr-tun-y	:= tun.o
> +obj-$(CONFIG_QRTR_MHI) += qrtr-mhi.o
> +qrtr-mhi-y	:= mhi.o
> diff --git a/net/qrtr/mhi.c b/net/qrtr/mhi.c
> new file mode 100644
> index 000000000000..2f604dff93cd
> --- /dev/null
> +++ b/net/qrtr/mhi.c
> @@ -0,0 +1,126 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (c) 2018-2020, The Linux Foundation. All rights reserved.
> + */
> +
> +#include <linux/mhi.h>
> +#include <linux/mod_devicetable.h>
> +#include <linux/module.h>
> +#include <linux/skbuff.h>
> +#include <net/sock.h>
> +
> +#include "qrtr.h"
> +
> +struct qrtr_mhi_dev {
> +	struct qrtr_endpoint ep;
> +	struct mhi_device *mhi_dev;
> +	struct device *dev;
> +};
> +
> +/* From MHI to QRTR */
> +static void qcom_mhi_qrtr_dl_callback(struct mhi_device *mhi_dev,
> +				      struct mhi_result *mhi_res)
> +{
> +	struct qrtr_mhi_dev *qdev = dev_get_drvdata(&mhi_dev->dev);
> +	int rc;
> +
> +	if (!qdev || mhi_res->transaction_status)
> +		return;
> +
> +	rc = qrtr_endpoint_post(&qdev->ep, mhi_res->buf_addr,
> +				mhi_res->bytes_xferd);
> +	if (rc == -EINVAL)
> +		dev_err(qdev->dev, "invalid ipcrouter packet\n");
> +}
> +
> +/* From QRTR to MHI */
> +static void qcom_mhi_qrtr_ul_callback(struct mhi_device *mhi_dev,
> +				      struct mhi_result *mhi_res)
> +{
> +	struct sk_buff *skb = (struct sk_buff *)mhi_res->buf_addr;
> +
> +	if (skb->sk)
> +		sock_put(skb->sk);
> +	consume_skb(skb);
> +}
> +
> +/* Send data over MHI */
> +static int qcom_mhi_qrtr_send(struct qrtr_endpoint *ep, struct sk_buff *skb)
> +{
> +	struct qrtr_mhi_dev *qdev = container_of(ep, struct qrtr_mhi_dev, ep);
> +	int rc;
> +
> +	rc = skb_linearize(skb);
> +	if (rc) {
> +		kfree_skb(skb);
> +		return rc;
> +	}
> +
> +	rc = mhi_queue_skb(qdev->mhi_dev, DMA_TO_DEVICE, skb, skb->len,
> +			   MHI_EOT);
> +	if (rc) {
> +		kfree_skb(skb);
> +		return rc;
> +	}
> +
> +	if (skb->sk)
> +		sock_hold(skb->sk);
> +
> +	return rc;
> +}
> +
> +static int qcom_mhi_qrtr_probe(struct mhi_device *mhi_dev,
> +			       const struct mhi_device_id *id)
> +{
> +	struct qrtr_mhi_dev *qdev;
> +	int rc;
> +
> +	qdev = devm_kzalloc(&mhi_dev->dev, sizeof(*qdev), GFP_KERNEL);
> +	if (!qdev)
> +		return -ENOMEM;
> +
> +	qdev->mhi_dev = mhi_dev;
> +	qdev->dev = &mhi_dev->dev;
> +	qdev->ep.xmit = qcom_mhi_qrtr_send;
> +
> +	dev_set_drvdata(&mhi_dev->dev, qdev);
> +	rc = qrtr_endpoint_register(&qdev->ep, QRTR_EP_NID_AUTO);
> +	if (rc)
> +		return rc;
> +
> +	dev_dbg(qdev->dev, "Qualcomm MHI QRTR driver probed\n");
> +
> +	return 0;
> +}
> +
> +static void qcom_mhi_qrtr_remove(struct mhi_device *mhi_dev)
> +{
> +	struct qrtr_mhi_dev *qdev = dev_get_drvdata(&mhi_dev->dev);
> +
> +	qrtr_endpoint_unregister(&qdev->ep);
> +	dev_set_drvdata(&mhi_dev->dev, NULL);
> +}
> +
> +static const struct mhi_device_id qcom_mhi_qrtr_id_table[] = {
> +	{ .chan = "IPCR" },
> +	{}
> +};
> +MODULE_DEVICE_TABLE(mhi, qcom_mhi_qrtr_id_table);
> +
> +static struct mhi_driver qcom_mhi_qrtr_driver = {
> +	.probe = qcom_mhi_qrtr_probe,
> +	.remove = qcom_mhi_qrtr_remove,
> +	.dl_xfer_cb = qcom_mhi_qrtr_dl_callback,
> +	.ul_xfer_cb = qcom_mhi_qrtr_ul_callback,
> +	.id_table = qcom_mhi_qrtr_id_table,
> +	.driver = {
> +		.name = "qcom_mhi_qrtr",
> +	},
> +};
> +
> +module_mhi_driver(qcom_mhi_qrtr_driver);
> +
> +MODULE_AUTHOR("Chris Lew <clew@codeaurora.org>");
> +MODULE_AUTHOR("Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>");
> +MODULE_DESCRIPTION("Qualcomm IPC-Router MHI interface driver");
> +MODULE_LICENSE("GPL v2");
> -- 
> 2.17.1
>