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x-ms-exchange-antispam-messagedata: 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 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: nxp.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: DB8PR04MB7162.eurprd04.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: 295a38f7-85ac-46bb-be05-08d835e79fd5 X-MS-Exchange-CrossTenant-originalarrivaltime: 01 Aug 2020 06:53:40.7331 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 686ea1d3-bc2b-4c6f-a92c-d99c5c301635 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: 1e+zxNL8Vg+D6ln3zseY10KWzt45JSBV63gMZHmnw07Sg9sgKYAh9CsAqEL7IguJ/AFVhYer+CCgd40sC1nkyg== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DB8PR04MB5755 Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org =20 >=20 > On 20-07-31 10:12:48, Alan Stern wrote: > > On Fri, Jul 31, 2020 at 02:06:20PM +0000, Peter Chen wrote: > > > On 20-07-31 14:25:20, Greg Kroah-Hartman wrote: > > > > On Fri, Jul 31, 2020 at 12:11:32PM +0000, Peter Chen wrote: > > > > > > > > Grab a reference from somewhere else and do not give it up for a > > > > long time. > > > > > > > > > > So wait_for_completion_timeout is suitable? The similar use case is > > > when we open the file at the USB Drive at Windows, and we click > > > "Eject", it will say "The device is currently in use", and refuse our= "Eject" > > > operation. > > > > > > When we try to remove the gadget, if the gadget is in use, we could > > > refuse the remove operation, reasonable? > > > > No, the real solution is to fix the UDC drivers. They need to > > allocate the gadget structure dynamically instead of reusing it. And > > they should have a real release routine that deallocates the gadget str= ucture. > > > > Alan Stern >=20 > So, the basic routine should like below. I thought the usb_gadget should = be > deallocated before the UDC driver remove itself (UDC device is the parent= of > usb_gadget device), I may not need to wrong about it, it is just a memory= region, it > could release later. >=20 > xxx_udc_release(struct device *gadget_dev) { > struct usb_gadget *gadget =3D container_of(gadget_dev, struct > usb_gadget, dev); > kfree(gadget); > } >=20 >=20 > xxx_udc_probe(pdev) > { > udc_priv_data =3D kzalloc(sizeof(*udc_priv_data), GFP_KERNEL); > gadget =3D kzalloc(sizeof(struct usb_gadget), GFP_KERNEL); > udc_priv_data->gadget =3D gadget; > ... > usb_add_gadget_udc_release(&pdev->dev, gadget, xxx_udc_release); >=20 > } >=20 > At xxx_udc_remove(pdev) > { > usb_del_gadget_udc(udc_priv_data->gadget); > /* need to never reference udc_priv_data->gadget any more */ > udc_priv_data other deinit; > kfree(udc_priv_data); > } >=20 > Since all structures xxx_udc_release uses are common one, it could replac= e > usb_udc_nop_release at udc/core.c. >=20 =20 Since gadget structure is allocated at UDC drivers, I think it should be fr= eed at the same place. Current common release function at udc/core.c may not a good idea per our discussion. Peter